International SMS gateway pricing is a real burden on a small company sending thousands of messages a month. There's a far cheaper option already in your pocket: your ordinary local SIM.
The idea
The Mersal app installs on an Android phone and becomes a bridge between your account and your SIM. The campaign is sent from the Mersal dashboard, and the app receives the instructions and sends the messages from the SIM exactly as if you were texting by hand — only automatically.
The cost difference
With an international provider you pay per message. With your SIM you pay your monthly bundle regardless of volume (within the bundle). For a business sending 2,000–5,000 messages a month, the difference is substantial.
The calculation that matters: divide your monthly bundle cost by the messages you actually send. If the bundle covers 3,000 and you send 3,000, your per-message cost is a fraction of any international provider. But if you only send 300, the bundle costs more than the provider would — so the maths depends on your bundle utilisation, not the headline price.
Limits you must know
- Throughput: a SIM sends one message after another, not thousands per minute. It's not suited to an urgent campaign to tens of thousands.
- Operator limits: mobile carriers impose daily caps, and exceeding them can suspend the line.
- No custom sender ID: the message arrives from your number, not your company name.
- Device dependent: it needs a phone on power and internet at all times.
- No true DLR: you know the message left, but delivery confirmation is weaker than a professional provider's.
Operator limits — where people get caught
Carriers watch patterns, not just counts. What raises the odds of a suspended line:
- Sending at a perfectly fixed rate (one message exactly every 5 seconds) — an obvious automated signature.
- The identical text to hundreds of numbers.
- Continuous sending around the clock with no pause.
- Repeatedly exceeding the bundle's daily cap.
The fix: enable randomised rather than fixed intervals, set a daily send window (say 9am–8pm), and leave headroom under the daily cap instead of hitting it exactly.
When to use it, and when not to
- Good fit: appointment reminders, order confirmations, notifications to a mid-sized customer base, small businesses cutting costs.
- Bad fit: OTP codes that must arrive in seconds, very large campaigns, anything needing an official sender ID.
Setup
- Download the Mersal Android app from the download page in your account.
- Link it to your account and select the SIM (if the phone is dual-SIM).
- Set rate limits to match your bundle and your operator's caps.
- Keep the phone on a charger and stable Wi-Fi, and disable battery optimisation for the app.
Keeping the bridge alive round the clock
The most common cause of a stalled bridge isn't a fault — it's Android suspending the app to save battery. The settings to get right:
- Disable "battery optimisation" for this app specifically in app settings.
- Enable "allow background activity".
- Pin (lock) the app in the recent-apps list so the system won't close it.
- On Xiaomi, Huawei and Oppo devices in particular there are "autostart" permissions that must be enabled manually.
- Letting the screen switch off is fine — but never reboot without confirming the app came back up.
Practical advice
Keep the app on a dedicated work phone, not your personal one. And monitor connection state from the dashboard — the app's "connected" flag doesn't always reflect reality, so treat the regular heartbeat as the real signal that the bridge is alive.
Troubleshooting
- Messages stuck in the queue: the app isn't connected. Open it on the phone and check the last heartbeat.
- Sends fine then stops after a few hours: battery optimisation is active. Check the autostart settings.
- Messages start failing suddenly: usually the daily bundle cap or an exhausted balance.
- The line was suspended by the carrier: reduce the rate substantially, vary the text, and speak to the carrier's support.
The best mix
There's nothing stopping you running both: Android SIM for routine, cost-saving messages, and a professional provider for OTP and critical sends. Mersal lets you define both and pick the gateway per campaign.
Frequently asked questions
Can I use more than one phone? Yes, and it raises your total throughput while spreading load across SIMs.
Does the app read my personal messages? It handles sending tied to your account; using a dedicated work phone settles the question entirely.
What if the internet drops? Messages stay queued and send once the connection returns.
