Why Replace Now
Aging PBXs, rising PRI/POTS costs, hybrid work, and new 911 rules make “do nothing” risky. Modern voice platforms deliver better uptime, analytics, and integrations—often for less than you’re spending to keep legacy gear alive.
Your Target Architecture Options
Cloud UCaaS (turnkey): Phones, softphones, voicemail, IVR, SMS, and analytics as a service. Fastest rollout, per-user licensing.
Microsoft Teams Phone / Zoom Phone (collab-first): Keep Teams/Zoom as the client; add PSTN via Operator Connect or Direct Routing.
On-prem IP PBX + SIP trunks (control): Keep hardware, replace PRIs with SIP for cost/flexibility.
Hybrid (practical bridge): Cloud for users, local gateways for analog, paging, and survivability.
Step 1 — Discover & Design (What You Have vs. What You Need)
Inventory & Numbers
DIDs/Toll-free, extensions, hunt groups, fax lines, door phones, paging, modems, alarms, elevators.
Pull CSRs (Customer Service Records) from carriers; verify which numbers live on which circuits.
Call Flows & Features
Main line/IVR scripts, departments, after-hours/holiday routing, voicemail trees, ring groups, queues, recordings, compliance holds.
Integrations
CRM screen-pops, call logging, contact center, call recording/quality, lobby phones, overhead paging/music.
Compliance & Safety
E911 (Kari’s Law, RAY BAUM’s Act): testable emergency routing, dispatchable locations per floor/suite, on-site notifications.
Network Readiness
LAN/WAN capacity, voice VLAN, QoS (DSCP), jitter/latency targets (<30 ms jitter, <150 ms one-way), PoE budget, Wi-Fi coverage for softphones.
Internet redundancy (fiber + 5G/4G) or SD-WAN for multi-site.
Step 2 — Choose the Build (Phones, SBCs, and the “Last 10%”)
Devices: desk phones vs. headsets/softphones; common-area and conference phones.
Analog/Specialty: fax (eFax or T.38 ATA), elevator/door phones (ATA or SIP intercoms), overhead paging (SIP paging amp), alarm panels (cell/IP communicators).
PSTN Edge: SBC/gateway for SIP security, interop, and local survivability.
Security: TLS/SRTP, least-privilege firewall rules, geo-blocks, fraud alerts.
Contact Center (if needed): queues, skills, WFM, call scoring, AI summaries.
Step 3 — Porting & Cutover Strategy (No Lost Calls)
Porting plan: Pick FOC date(s), decide flash cut vs. phased (pilot DID blocks first).
Call forwarding safety net: temporary forwards during port windows.
Number hygiene: consolidate carriers, retire unused DIDs, document routing.
Acceptance criteria (define now): what must pass before you decommission the old PBX.
Step 4 — Pilot, Train, and Stage
Pilot 10–15% of users and at least one site. Validate call flows, headsets, softphones, and Wi-Fi.
User training: 30-minute live sessions + quick reference guides (voicemail, transfer/park, mobile app).
Staging: pre-provision phones, assign E911 locations, label ports, confirm PoE and VLAN.
Step 5 — Cutover Week (Checklist You’ll Actually Use)
Day –3 to –1
Confirm port orders and FOC with carriers.
Record IVR prompts, upload schedules/holidays.
Final QoS checks; failover test (kick SD-WAN/LTE).
FOC Day
Watch for partial ports; toggle temporary forwards.
Validate inbound/outbound across all key paths.
Acceptance Tests (sample)
Inbound: main, departments, toll-free → ring groups/queues, after-hours, voicemail.
Outbound: local/LD/international restrictions, caller ID branding.
E911 test (non-emergency PSAP route) → verify dispatchable address and notifications.
Analog: lobby/elevator phones, paging, fax send/receive.
Contact center: queue behavior, recordings, wallboards.
Resiliency: kill WAN → confirm LTE/backup calls and local survivability.
Decommission
Cancel PRIs/POTS/circuits after acceptance; archive CDRs/voicemail as required.
Timelines & Budget (Real-World)
Typical timeline: 4–6 weeks for single-site, 6–12 weeks for multi-site.
Costs: licenses (per user/capacity), phones/headsets, SBC/gateway (if needed), porting, professional services.
Savings levers: retire PRIs/POTS, right-size licenses, BYOD headsets, eFax, consolidate carriers, turn on analytics to improve staffing.
Common Pitfalls (and How We Avoid Them)
Forgetting the “weird” lines: elevator/door/paging/fax—solve with ATAs or SIP endpoints up front.
Under-testing E911: we script PSAP test calls and document results per site.
QoS left to chance: we mark DSCP, segment voice VLANs, and validate jitter/packet loss with live probes.
Train-then-go: short, role-based training and floor support on cutover week.
How AtoZ ISP Runs Your Migration
Discovery & CSR audit → clean number plan.
Design & vendor fit → UCaaS / Teams / Zoom / SIP to IP-PBX.
Network readiness → VLAN/QoS, SD-WAN/failover, security hardening.
Porting PMO → carrier pushes, FOC orchestration, acceptance testing.
Analog strategy → ATAs/SBCs for paging, doors, fax, alarms.
Aftercare → admin training, MACD process, monthly analytics.
Thinking about moving off a legacy PBX?
Send us your site count, carrier list, and a copy of your current call flow. We’ll return a one-page migration plan with timelines, risks, and a clear budget.
