Key Takeaways
- A scheduled SMS is a job the control plane holds until fire time. GSM still needs a charged, paired Android at that second.
- Store send time in the recipient’s timezone. A 09:00 UTC reminder is a 02:00 complaint in another city.
- Re-check STOP, cancelled appointments, and balance at fire — not only at enqueue.
- Quiet hours belong on promo lanes. OTP should not sit in a six-hour scheduler.
- Priced by devices and SMS send volume. You use your own phone and operator SMS credit. Queued jobs still debit airtime when they fire.
What a schedule actually is
Product: scheduled SMS. The control plane stores when to send. The Android radio still submits the PDU. If the handset is offline, OEM-killed, or out of airtime at fire, you have a missed job — not a retry fairy. Sibling: schedule campaigns by timezone.
A reminder queued on Thursday for Monday 09:00 is a bet that the phone, the SIM, and the consent flag all survive the weekend.
Practice table
| Practice | Do | Do not |
|---|---|---|
| Timezone | IANA on the contact | Server local, “Pakistan = UTC+5 forever” |
| STOP | Re-check at fire | Honor only at CSV import |
| OTP | Send now | Park codes in the scheduler |
| Promo | Quiet hours + STOP footer | 06:12 Sunday “just listed” |
| Device | Charged, exempted, nicknamed | Founder’s daily driver that leaves the office |
Recipient timezone, not UTC theatre
Multi-country lists need per-row zones. DST still happens. Educational timezone data: IANA time zone database. Contacts: contacts and lists.
Re-check STOP at fire time
Someone will reply STOP on Saturday. Monday’s queued blast must skip them. Auto-reply and STOP. Cancelled appointments belong in the booker, not as a ghost SMS — transactional pattern: transactional SMS.
Ship a schedule that survives night
- Pick the feature, not a cron on your laptop. Use scheduled SMS so fire time is in the control plane. Laptop sleep is not a scheduler.
- Stamp timezone on the contact. IANA zone, not a country guess. DST exists.
- Set quiet hours per lane. Promo silent overnight. Transactional reminders can be tighter. OTP is now, not queued.
- Re-evaluate at fire. STOP, cancelled slot, depleted SIM, unpaired device → skip, do not blast anyway.
- Canary a 10-minute job. Staff number, DLR, reboot the phone in the wait window, confirm skip vs send policy.
- Watch OEM overnight. A 07:00 fire after a 02:00 battery kill is a missed clinic list.
Pairing: device setup. API: SMS API documentation.
The phone must be awake
OEM battery, Wi-Fi isolation, and a charger that fell out at 02:00 dominate scheduled reliability. Dual SIM will not save a sleeping chassis. Isolate promo schedules from the OTP device via multi-device.
Cost shape
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. Jobs that fire still count toward platform volume and airtime. Free is 300 SMS lifetime for canaries. Paid from $19/month. Device and SMS volume pricing.
Next steps
Timezone on the row, STOP at fire, OTP off the scheduler, and a phone that will still be plugged in on Monday.
Related product pages
Jump to the live product docs for this topic—not another long-form article.
- scheduled SMS campaignsSend later windows
- SMS API documentationLive endpoint reference
- device and SMS volume pricingPlans and allowances
- Android SMS gateway product guideDefinition, product, and how to buy
