Migrating From Per-Minute SIP Trunks to Flat-Rate

Why the Switch Makes Sense at Scale

Per-minute pricing is a volume tax. At $0.01/min (a common blended US rate), a single agent working a 7-hour shift clocks 420 minutes of dial time — $4.20 per agent per day before carrier surcharges. Add regulatory recovery fees, CNAM dips, and mid-month rate adjustments, and that $0.01/min becomes $0.014–$0.018 effective.

Flat-rate trunking converts a variable cost center into a fixed line item. Your finance team can budget it; your operations team can stop auditing CDRs for billing anomalies.

The crossover point for US/CA (UnlimCall at $5/agent/day) against a $0.015/min blended rate is roughly 5.5 hours of connected call time per agent per day. Most outbound call centers exceed that by the early afternoon.

Pre-Migration Evaluation Checklist

Before you submit a porting request or redirect a trunk, work through these items in order.

1. Audit Your Current Usage

• Pull 90 days of CDRs from your existing carrier. Segment by agent, by time of day, and by destination country.
• Calculate your effective per-minute rate (total charges ÷ total minutes). Include all line items — taxes, surcharges, minimum charges.
• Identify your top 5 destination countries by volume. Make sure the flat-rate provider serves them.

2. Map Your Caller ID Requirements

• List every outbound number in use and which markets it represents.
• Determine whether your numbers are ported (owned by you) or provided by the carrier. Carrier-provided numbers cannot be ported; you will need new numbers provisioned on the new platform.
• For US/CA campaigns, confirm that your numbers are STIR/SHAKEN-capable or factor in the answer-rate impact of unsigned calls.

3. Verify SIP Compatibility

• Confirm your dialer or PBX supports standard SIP over UDP, TCP, or TLS. Most predictive dialers and CCaaS platforms do.
• Request the new provider's SIP host addresses and test registration in a non-production environment before cutover.
• Check codec support. G.711 (PCMU/PCMA) is universal. If you use G.729 for bandwidth efficiency, verify the provider supports it.

4. Test in Parallel — Do Not Hard-Cut

• Route 10–15% of outbound traffic to the new trunk while keeping your existing trunk active.
• Monitor post-dial delay, audio quality (MOS if your monitoring stack supports it), and answer seizure ratio (ASR) for at least 5 business days.
• Compare CDR-level call disposition data between old and new legs. Drops, busy signals, and SIT tones should be at parity or better.

5. Number Porting

• If you own your numbers, initiate a LOA (Letter of Authorization) and CSR (Customer Service Record) request with your losing carrier. US/CA ports typically complete in 5–10 business days for standard geographic numbers; toll-free can take longer.
• For international numbers, porting feasibility varies by country and losing carrier. In markets where porting is restricted or slow, your fastest path is provisioning new local numbers and running a brief parallel period.
• Never port your numbers before completing parallel testing. A failed port with no fallback trunk is a full outage.

6. Update Your Dialer Configuration

• Point your SIP trunk to the new provider's gateway.
• Update your outbound caller ID to one of your provisioned numbers on the new platform.
• Retest your dialer's pacing, DTMF pass-through, and call recording integrations.

7. Final Cutover

• Schedule cutover outside peak dialing hours (early morning or weekend).
• Keep the old trunk active for 48 hours post-cutover as a fallback.
• Monitor answer rates, ASR, and agent-level metrics for the first full business day.

Cost-Comparison Worksheet

The table below uses a 20-agent team dialing into the US, 22 business days per month, 7 connected hours per agent per day.

Assumptions: 7 connected hours = 420 min/agent/day; blended rate $0.015/min; surcharges 15%; CNAM $0.002/dip × 3 dips/hr. Your numbers will differ — run the same formula against your actual CDRs.