Choosing a SIP carrier — 5 questions to ask

Most SIP trunk pages list the same things: per-minute rate, country coverage, channel pricing. Those matter, but they're commoditized. Here's what actually separates good from bad.

1. What's their per-minute rate to your top 10 destination prefixes?

The headline rate is meaningless. Carriers cross-subsidize: cheap to NYC, expensive to rural NM. Ask for the rate at the NPA-NXX level for the prefixes you actually dial.

If your campaigns target 50 area codes, ask for the rate-deck CSV. Real carriers will send it; resellers will hedge.

2. What's their CLI / Caller-ID policy?

You're going to need to set caller ID per campaign. Ask:

• Can I bring my own DID and use it as outbound CLI?
• Do you support SHAKEN/STIR attestation? (Mandatory in the US since 2021.)
• What level of attestation will my calls receive — A, B, or C? B and C are death for answer rates.

If they don't know what STIR attestation is, walk away.

3. How fast do they answer abuse / fraud tickets?

Outbound dialing → at some point a number gets reported as spam → carrier suspends your trunk. Question is how fast they unsuspend.

Ask:

• What's your typical response time for an abuse ticket?
• Who reviews — automated or human?
• How do I appeal a suspension?

A good carrier responds in hours. A bad one suspends Friday afternoon and you're down for the weekend.

4. What's their POPs map?

Latency from your VICIdial server → carrier ingress matters for audio quality. Ask where their SIP-handling POPs are. A carrier with US-East / US-West / Europe / Asia is fine. A carrier with one US-Central POP and you're dialing internationally — problematic.

Match your VICIdial server region to a region the carrier has a POP in.

5. What's the dispute policy on suspended/terminated calls?

Some carriers bill for reattempts, "completed" calls (which actually went to voicemail), and short calls (under 6 seconds) at full rate. These costs add up fast at predictive-dial volumes.

Read the fine print — in particular:

• Minimum billable duration (1s? 6s? 60s?)
• "Connected" vs "answered" billing
• Surcharges for international, mobile, premium-rate

Carriers our customers commonly use

(Not a recommendation — and we don't take referral fees.)

• Twilio — easy to start, expensive at scale, excellent dashboards.
• Telnyx — better rates than Twilio, strong API, US/Europe POPs.
• Bandwidth — direct US carrier, good rates for high-volume domestic.
• Voxbeam — Europe/Asia coverage, competitive rates, smaller dashboard.
• Ringbridge / Inteliquent / Plivo / Sinch — also worth quoting.

How to test before you commit

Run a 200-call pilot through a candidate carrier. Track:

• Answer rate
• Audio quality (have agents rate 1-5)
• Average call setup time (time to "ringing")
• Per-minute cost vs quoted

A good carrier survives the pilot. A bad one shows the seams.