Unified IP PBX Deployment for a Multi-Branch Commercial Bank: 60% Reduction in Inter-Branch Call Costs

Each of the bank's 28 branches maintained its own independently contracted PSTN landline service, typically two to four lines per branch from Teletalk or BTCL, supplemented in some branches by private operator lines from Banglalink or Robi for staff use. There was no unified telephone system — a customer calling the Sylhet branch could not be transferred to a colleague in Dhaka; inter-branch communication happened through personal mobile phones, which were unrecorded, unsecured, and billed to the bank's general mobile expense account.

The bank's finance team conducted a telecom expense analysis in late 2025 that revealed the full cost picture. Total monthly PSTN line rental and call charges across 28 branches averaged BDT 85,000. The largest single cost component — approximately BDT 40,000 per month — was calls between branches and the head office: operational calls from branch managers to HQ departments, loan approval follow-ups, compliance reporting calls, and customer query escalations. These calls were charged at standard operator rates because they traversed the public telephone network, even when both parties were on the same bank's premises connected by the same bank's MPLS network.

Beyond cost, the absence of call recording was an increasing compliance concern. Bangladesh Bank's ICT Guideline v4.0 references call recording for customer-facing teller and service desk lines. The bank's internal compliance team had flagged in two consecutive internal audit cycles that teller counter telephone calls — during which customers sometimes provided account instructions, loan repayment commitments, or account detail changes verbally — were unrecorded. In the event of a customer dispute over a verbal instruction given by phone, the bank had no evidence of what was said.

Conference calling capability was similarly absent. Branch managers participating in the weekly national operations call had to be physically present at head office, or listen individually via their mobile phones — a cumbersome arrangement that limited participation, especially for managers at Chittagong and Sylhet who faced significant travel time. The CEO had repeatedly raised the conference calling gap in operations meetings as a symptom of the bank's outdated communications infrastructure.

The bank's IT department had moved most inter-branch data traffic to an MPLS network in 2022, which meant the physical connectivity to carry VoIP between branches was already in place. The economics of IP telephony — free inter-branch calls over the existing MPLS — made an IP PBX migration highly attractive on paper. What had prevented action was uncertainty about implementation complexity and concern about disrupting branch telephone service during transition.

SSAL designed and deployed a centralized IP PBX architecture with the Yeastar P560 as the core platform, connecting all 28 branches under a single unified communications system.

Core PBX — Yeastar P560: The Yeastar P560 Enterprise IP PBX was installed at the bank's head office in Dhaka, in the IT server room. The P560 supports up to 500 concurrent users, 60 concurrent calls, and built-in call recording with local or NAS storage. It provides an intuitive web-based administration interface and integrates natively with SIP trunking providers for PSTN gateway. The P560's built-in redundancy features — automatic failover to a secondary SIP trunk if the primary fails, and local survivability configuration for branches — addressed the bank's concern about service continuity.

IP Phones — Yealink T54W: 168 Yealink T54W IP phones were deployed across all 28 branches at a rate of 6 phones per branch (teller counter, branch manager, assistant manager, customer service desk, loan officer, and operations staff). The T54W is a 16-line colour-display business phone with WiFi and Bluetooth, supporting HD audio and Busy Lamp Field (BLF) for monitoring colleague availability. The phone's HD audio codec was important for teller counter use — ensuring that customer instructions received by phone were clearly audible and intelligible for the call recording.

SIP Trunk — Link3 Technologies: A dedicated SIP trunk with 20 simultaneous call capacity was provisioned from Link3 Technologies, Bangladesh's largest ISP and an established SIP trunk provider with direct interconnect to BTCL for nationwide PSTN origination and termination. The SIP trunk replaced all 28 branches' individual PSTN lines. Incoming DDI (Direct Dial-In) numbers were allocated per branch, preserving each branch's existing published telephone numbers — customers dialling the existing branch number continue to reach the same branch without any awareness of the backend change.

MPLS QoS Configuration: SSAL's network team worked with the bank's MPLS provider to configure DSCP marking and QoS queuing for VoIP traffic at all 28 branch routers. Voice traffic was assigned to a priority queue with guaranteed bandwidth allocation of 512kbps per branch — sufficient for 5 simultaneous HD VoIP calls — and maximum latency of 50ms and jitter of 20ms enforced. This ensured that a spike in core banking data traffic at peak periods could not degrade call quality.

Call Recording: The Yeastar P560's built-in call recording module was configured to automatically record all inbound and outbound calls on the 28 designated teller counter and customer service extensions. Recordings are stored on a dedicated NAS device at head office, retained for 90 days, and searchable by extension, date, time, and call duration via the Yeastar web interface. Access to the recording archive is restricted to the bank's Compliance Officer and Head of Operations, with an audit log of all recording access events.

Conference Calling: The P560's built-in conference bridge was configured with 10 permanent conference room extensions — each supporting up to 20 participants — allocated to the bank's weekly operations calls, divisional manager calls, and ad-hoc conference use. Branch managers can join conference calls from their Yealink desk phones or from the Yeastar mobile app on their smartphones.