Key Takeaways
- Prepaid dies silently at 02:00. Postpaid surprises finance at month-end. Pick the failure you can staff.
- OTP and reminders want a SIM that will still submit on Monday. Promo experiments can live on prepaid if someone tops up.
- Register the line in the org’s name. Contractor leftover prepaid is a shutdown.
- Dual SIM is not two billing domains if both slots share one battery.
- Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Operator airtime is never included in the plan fee.
The SIM is the real SLA
Longer field guide: prepaid vs postpaid SIMs. App-flavored sibling: how to choose prepaid vs postpaid. This core spoke is production: which failure you staff for. How an Android SMS gateway works.
A prepaid OTP SIM is a countdown timer someone forgot to calendar.
Prepaid vs postpaid for a gateway
| Prepaid | Postpaid | |
|---|---|---|
| Empty | Hard stop, often silent | Cap / bill shock |
| KYC | Easy to leave in a contractor’s NID | Usually org-billed — still inventory ICCID |
| OTP | Only with auto-reload + pager | Usually better |
| Promo experiments | Fine if topped up | Watch A2P fair-use |
| Expiry packs | 7/30/90-day traps | Contract term instead |
OTP wants a boring bill
OTP verification. Isolate: multi-device. USSD balance checks: USSD — do not poll *123# from the auth phone every minute.
Pick and operate the SIM
- Split lanes first. Auth vs promo. Then assign prepaid or postpaid per lane, not one SIM “for everything.”
- Prefer postpaid (or auto-reload) for OTP. Empty prepaid is a login outage. Balance USSD is a ritual, not a pager.
- KYC in the org’s name. Keep ICCID inventory. When the contractor leaves, the SIM should not.
- Alert on balance and last DLR. Prepaid: days-to-empty. Postpaid: cap warnings. Both: pairing light.
- Spare SIM in the drawer. Already registered, already tested. Dual SIM is not that spare.
- Re-canary after a plan change. Operator “upgrades” change A2P filtering. Staff numbers, not customers.
Pairing: device setup. Operator cost worksheet: estimate monthly operator cost.
KYC, expiry, and whose name
Biometric SIM rules are local (PTA, BTRC, operator). We do not waive them. Tourist prepaid is not a production CLI.
Two invoices
Service pricing is based on device count and total SMS sent through the gateway. You need a working Android phone with a SIM and SMS credit from your mobile operator. Operator message costs are yours—we do not sell carrier SMS balance. Paid from $19/month; Free 300 SMS lifetime. Device and SMS volume pricing. Prepaid top-ups and postpaid GSM are the other ledger.
Next steps
Auth on a line that cannot silently die, promo on a line you watch, ICCIDs in a doc, spare already registered.
Related product pages
Jump to the live product docs for this topic—not another long-form article.
- SMS API documentationLive endpoint reference
- device and SMS volume pricingPlans and allowances
- Twilio vs Android SMS gatewayCloud vs own-SIM cost model
- Android SMS gateway product guideDefinition, product, and how to buy
