Rewriting a telecommunications provider's in-app calling system

A telecommunications provider outgrew its own agent CRM as its customer base scaled

The client is a telecommunications provider running a modular internal CRM across its call center, marketing, and field service teams. Customer service depends on that CRM for almost every interaction, and agents are on calls for most of the working day, so the reliability of the calling layer directly determines how much customer contact the business can handle.

Fragmented data and an unstable calling integration were costing agents time on every call

• The original in-app calling integration was built quickly with AI assistance and left an unstable codebase. New bugs surfaced daily, at times dozens of reports a day, and the volume consumed engineering time that should have gone to new work. Fixing the visible bug rarely addressed the underlying cause, so the same class of failure kept returning.

• Call handling depended on a single browser tab. Agents working across several open CRM tabs lost active calls when the tab holding the call connection was closed, a workflow failure with a direct cost in dropped customer contact.

The measurable main targets that defined the rebuild: zero bugs and stable calls

• Eliminate the daily bug volume by rebuilding the calling integration cleanly instead of patching it.

• Move agents off physical phones onto an in-app calling experience.

• Remove the browser-tab dependency causing dropped calls

The rewrite was a deliberate technical call. Rather than keep patching an unstable integration, the team paused incoming business requests and rebuilt the voice integration from the ground up on NestJS. Client stakeholders were initially reluctant to stop feature work for a rewrite; the engineering lead held the line, and the internal manager backed the decision once the results came in.

To fix the dropped-call problem, the team built a companion Chrome extension that moves call handling out of the CRM tab structure entirely, so closing a tab no longer ends a live call. The extension has been delivered and is ready for rollout; the client had not yet adopted it in production as of the engagement.