Updated: Sep 22, 2025
You moved meetings and chat to the cloud years ago. The switchboard stayed on PBX shelves and PRI trunks. The monthly bill looks tidy, then quarter-end hits in Delhi and PRI channels max out, a fibre cut in Chennai takes a store dark, and your team spends nights on moves and changes. The real question is not the list price. It is time to open sites, risk when things break, and the hours your engineers lose to keep the voice alive.
PBX needs you to size for the spike. You buy controllers, gateways, cards, and PRIs that sit idle most weeks. Resilience means duplicates. Changes queue behind specialists. When you add a site in Bengaluru, you stage gear, ship spares, and pray the carrier turns up on time. All of that is cost; it just does not show on a single line item.
Cloud calling moves call control, routing, recording, and policy into software. Users get soft clients, you keep IP phones where they help, you connect to PSTN by cloud carrier options or your telco through certified SBCs. Capacity becomes a setting, not hardware. New queues and IVR prompts go live in minutes. Quality is visible across ISPs. Admins use SSO with MFA, and every change leaves an audit trail.
Gurugram logistics, 900 users. Goal: kill PRI cost and raise answer rates in yards. Action, port DIDs to a certified cloud PSTN, bind users to Azure AD, deploy soft clients on rugged Androids, keep 120 IP phones for gates, and enforce TLS and SRTP. Month one, missed calls at shift change fell 38% and two racks of PBX gear were retired.
Chakan auto supplier near Pune, 350 users. Goal: bilingual IVR for dealers and zero voice outages during dispatch. Action, SIP to two carriers through certified SBCs in different regions, percountry dial rules, SRTP media, and cellular failover at the plant edge. Outcome: IVR containment moved up and calls stayed online through two fibre cuts.
If you run a single site with sunk PBX cost, stable volume, and hard analogue ties you cannot remove for two years, staying put can be cheaper nearterm. For net new sites or any plan that involves expansion across cities, cloud calling wins on time, risk, and total cost.
Insist on TLS 1.2 or higher for signalling and SRTP for media. Enforce MFA on admin changes. Set fraud limits and alerts by country. Ask for per-user quality metrics, packet loss, jitter, latency, and MOS, across all ISPs. Feed logs to your SIEM so you spot patterns early. These are not extras; they protect the savings you expect.
Count named users who take calls, include peak temps. List PRIs and SIP trunks, by site and carrier. Add PBX support, spares, power, space, and monthly engineer hours. Add downtime cost per hour for sales and service, use your own number. Price cloud calling as named users plus usage, include SBC cost if you bring your telco. Model a staged migration that keeps interop during porting so finance does not go dark on cutover day.
Independent signals back the shift. Ofcom’s PSTN switch-off guidance explains why TDM ends and IP interconnect is the path forward. IBM’s Cost of a Data Breach shows how outage and slow response magnify the impact. Use both as context in board packs, then trend your own numbers.
If you open sites in Delhi, Pune, Bengaluru, Hyderabad, or Chennai, if you change queues monthly, and if you want audit-ready logs without rack builds, cloud calling will save more money and time. PBX has a place only where growth is flat and analogue is immovable. The centre of gravity has moved.
As a Cisco Gold Partner, Proactive designs PBX exit plans that keep finance reachable on port day. We plan hybrid periods with clean routing between old and new dial plans, set quality thresholds your NOC can run, and leave a runbook your team owns.
Move faster, spend smarter. Book a 60-minute cloud calling cost session. You leave with a side-by-side cost model, a phased porting plan, and a quality checklist. Write to [email protected].
