Custom Call Center and Contact Centre Software Development
We build cloud call centers and omnichannel contact centres around your routing, campaigns and customers: voice, WhatsApp, email and SMS in one agent desktop, with AI where it helps. No per-seat licences, and the code is yours.
- years in VoIP
- 9+
- years in VoIP
- clients
- 100+
- clients
- channels in one agent desk
- 5
- channels in one agent desk
- countries
- 30+
- countries
- Channelsphone numbers, WhatsApp, social, email, SMS, chat
- Telephony layerSIP trunks, SBC, Asterisk or FreeSWITCH
- Routing engineskills, priorities, queues, SLAs
- AI layervoice agents, chatbots, transcription
- Agent desktopWebRTC softphone, inbox, CRM screen-pop
- Reporting and integrationsdashboards, CRM, help desk, data warehouse
Quick answer
What is call center software development?
Call center software development is building your own platform for handling customer calls and messages instead of renting per-seat software. CelloIP builds cloud call centers and omnichannel contact centres on Asterisk and FreeSWITCH: routing, IVR, dialers, WhatsApp, email and SMS, AI agents, dashboards and CRM integration. You own the code.
What we build
Start with the channels and teams you have today and add the rest in phases.
Inbound call center
ACD with skills-based routing, IVR, queues with callbacks, call recording, and a browser agent desktop with customer screen-pops.
Outbound campaigns and dialers
Preview, progressive and predictive dialers with list management, retry rules, answering-machine detection, calling windows and do-not-call checks.
Omnichannel contact centre
Voice, WhatsApp, Instagram and Messenger, email, SMS and web chat in one agent desktop, with one conversation history per customer.
SLA, ticketing and case management
Every call and message linked to a ticket, SLA timers and escalations, or integration with the help desk you already use.
AI agents and agent assist
AI voice agents and chatbots for tier-1 contacts, plus live transcripts, suggested answers and automatic call summaries for human agents.
Supervisor dashboards and reporting
Live wallboards, listen, whisper and barge, quality scoring, and historical reports on service level, handle time and campaign results.
Preview, progressive or predictive dialer?
Most outbound teams need more than one mode. We build all three and let supervisors choose per campaign.
| Mode | How it works | Best for | Watch out for |
|---|---|---|---|
| Preview | The agent sees the record, then chooses to dial | High-value or complex calls, B2B | Lowest risk of abandoned calls |
| Progressive | Dials the next number as soon as an agent is free | Steady campaigns, renewals, follow-ups | No abandoned calls by design |
| Predictive | Dials several numbers per free agent, predicting answer rates | High-volume campaigns with large lists | Needs abandonment control (in the US, 3% or less per campaign over 30 days) |
Related: TCPA rules for outbound calling · answering machine detection
Build or buy?
Packaged cloud contact centres are quick to start, but you pay per agent every month and work within their limits. A custom platform costs more up front and less as you grow.
Want a ready-made, white-label contact centre instead? Our sister company Sheerbit offers one as a product.
- You have dozens or hundreds of agents, so per-seat fees add up
- Your routing, campaigns or screens don't fit a packaged product
- Recordings and customer data must stay in a region or on your servers
- You want to resell the contact centre to your own customers
- You need deep integration with in-house systems
How much does custom call center software cost?
Typical project ranges by type of build. You get a fixed quote after discovery. Hosting, SIP trunks and channel fees (for example WhatsApp conversation charges) are separate running costs.
| Type of build | Typical scope | Typical range | Timeline |
|---|---|---|---|
| Voice call center | Inbound and outbound voice on Asterisk or FreeSWITCH: ACD, IVR, recording, agent softphone, supervisor dashboard, one CRM integration | $20,000 – $50,000 | 8–14 weeks |
| Omnichannel cloud contact centre | Voice plus WhatsApp, social, email and SMS, campaigns and dialers, SLA and ticketing, multi-tenant if you resell it | $50,000 – $150,000 | 4–8 months |
| Enterprise or AI-first contact centre | Hundreds of agents across sites, AI agents on tier-1 traffic, workforce management, data residency, migration from a legacy platform | Scoped after discovery | Agreed in the project plan |
Ways to work with us
Fixed-scope project
A defined platform delivered against agreed scope, milestones and acceptance tests.
Dedicated VoIP developer
A contact centre engineer working inside your team, backed by a 30-day money-back guarantee.
Build, then run
We build the platform, then host, monitor and extend it. Voice servers we operate run at 99.99% uptime.
How we build a contact centre
- 1Weeks 1–2
Discovery
Agents and sites, channels, call and message volumes, campaigns, systems to connect, rules you must follow and current pain points.
- 2Weeks 2–3
Design
Routing and campaign logic, agent and supervisor screens, architecture, capacity plan and migration plan.
- 3From week 3
Build in phases
Voice first, then each channel, dialer and integration, with a working staging system every sprint.
- 4Before full launch
Pilot
Load tests above expected peak, then one team or campaign live, with daily fixes from agent feedback.
- 5Ongoing
Roll-out and run
Team-by-team roll-out, training, monitoring and new features such as AI agents once the core is stable.
Project outcomes and client reviews
Client names are kept private. Reviews are quoted word for word from our Upwork profile.
Project outcome · Omnichannel contact centre
Built an omnichannel contact centre with inbound and outbound campaigns, and WhatsApp, Instagram, email and SMS handled in one agent desktop alongside voice, with SLA tracking and ticketing.
- Inbound and outbound campaigns
- WhatsApp and Instagram
- Email and SMS
- SLA rules and ticketing
Project outcome · Telephony core
Built a custom PBX platform handling 1,000+ concurrent channels, 50,000+ extensions and 50,000+ DIDs: the scale of telephony layer a large contact centre runs on.
“Great experience working with Kaushik. He provided valuable insights, quick solutions, and a clear understanding of VoIP infrastructure.”
“It was a pleasure working with Kaushik and the rest of the knowledgeable team at Celloip. I would highly recommend them for anyone looking for expertise in the VoIP, cellular or mobile application field.”
Built for the rules you work under
- Consent, do-not-call and calling-window checks on every campaign
- Abandonment-rate control on predictive campaigns
- Recording notices and pause-and-resume recording during card payments
- Role-based access and audit logs for agents and supervisors
- TLS and SRTP encryption for calls, and encryption for stored recordings
- Data hosted in the region or on the servers you choose
Frequently asked questions
What is call center software development?
It is designing and building your own platform for customer calls and messages: routing, IVR, dialers, agent desktop, recording, reporting and integrations. Instead of paying per agent for a packaged product, you own the software and can shape it around your processes and customers.
How much does custom call center software cost?
As a guide, a voice call center with ACD, IVR, recording and a CRM integration is typically $20,000–$50,000 over 8–14 weeks. An omnichannel cloud contact centre with campaigns, WhatsApp, email, SMS, SLAs and ticketing is typically $50,000–$150,000 over 4–8 months. Enterprise and AI-first builds are scoped after discovery. Hosting, SIP trunks and channel fees are separate running costs.
Build or buy: when does a custom contact centre make sense?
Packaged cloud contact centres are quick to start but charge per agent every month and limit how far you can change routing, screens and integrations. A custom build makes sense when you have many agents, unusual workflows, strict data rules, or want to sell the platform to your own customers.
What is a predictive dialer and is it legal?
A predictive dialer calls several numbers for each free agent and connects only answered calls, based on predicted answer rates. It is legal in most countries with conditions. In the US, the TCPA and FCC rules require consent for many calls and limit abandoned calls to 3% per campaign over 30 days. We build abandonment control, calling windows, consent and do-not-call checks into every dialer.
Can you add WhatsApp, email and social channels?
Yes. We connect the WhatsApp Business Platform, Instagram and Messenger, email, SMS and web chat into the same agent desktop and routing engine, so each customer has one history across channels. We have delivered this for an omnichannel contact centre with campaigns, SLAs and ticketing.
How do AI agents fit into a contact centre?
AI voice agents and chatbots handle routine contacts such as order status, bookings and FAQs, and hand over to a person with the context when needed. For human agents, AI adds live transcripts, suggested answers and automatic summaries. We add AI once the core routing is stable, starting with one use case.
Which CRMs and help desks can it integrate with?
We integrate with CRMs and help desks such as Salesforce, HubSpot, Zoho, Freshdesk and Zendesk, and with in-house systems through their APIs: screen-pops on incoming contacts, click-to-call, automatic logging of calls, dispositions and recordings.
Asterisk or FreeSWITCH for a call center?
Both work well. Asterisk is very flexible for queues and IVR-heavy designs; FreeSWITCH handles high concurrency and conferencing well. Large platforms often put Kamailio or OpenSIPS in front of either. We choose per project based on volume, features and your team's skills.
Who owns the platform?
You do. Source code, configuration and deployment scripts are handed over, and recordings and customer data stay in accounts or on servers you control. NDAs are signed before discovery.
Related services and guides
Custom PBX Development
The telephony core: IP PBX and multi-tenant cloud PBX platforms.
AI Voice Agent Development
AI agents that take tier-1 calls and hand over to your team.
AI Chatbot Development
RAG chatbots for WhatsApp, web chat and email in the same desk.
Call Centres and BPOs
How we work with contact centre operators and BPOs.
WebRTC Development
Browser softphones and video for agent desktops.
VoIP Billing Software
Usage rating and invoicing if you resell the platform.
Tell us about your contact centre
Share your agent count, channels, campaigns and the systems you use today. We'll reply with a recommended architecture, a phased plan and a fixed quote.
Contact CelloIPHiring instead? See VoIP developers.