sms updates

mkdocs/docs/docs/admin/broadcast/sms.md

@@ -394,6 +394,28 @@ export SMS_API_SECRET='your-generated-key'
 echo 'export SMS_API_SECRET="your-key"' >> ~/.bashrc
 ```
 
+### RCS / Chat Features interfering with replies
+
+**Symptoms:** You send SMS messages successfully but some or all replies never appear in the system. Recipients say they replied, but the conversation shows no inbound messages.
+
+**Cause:** Google Messages enables **RCS (Rich Communication Services)** by default. When RCS is active, replies from recipients who also have RCS may be sent over data/Wi-Fi instead of the carrier SMS channel. The Termux server only reads the SMS inbox via `termux-sms-list`, so RCS messages are invisible to it.
+
+**Fix:** Disable RCS on the SMS phone:
+
+1. Open **Google Messages** on the phone
+2. Tap the profile icon (top right) → **Messages settings**
+3. Tap **RCS chats** (or "Chat features")
+4. **Turn off** "Turn on RCS chats"
+
+!!! warning "This must be done on the phone running the SMS server"
+    Disabling RCS on the server phone forces all outgoing messages to use plain SMS, and ensures replies also come back as SMS. You do not need recipients to change anything on their end — when the server phone sends a plain SMS, the reply will be plain SMS as well (unless the recipient's carrier forces RCS-only, which is rare).
+
+**Additional checks:**
+
+- Some carriers (e.g. Google Fi, Jio) enable RCS at the carrier level. If disabling in the app doesn't help, contact the carrier to disable RCS on the SIM.
+- If the phone has **Samsung Messages** instead of Google Messages, go to Samsung Messages → Settings → Chat settings → turn off.
+- After disabling RCS, restart the phone and verify by sending a test message — the send button should show an **SMS** label, not "Chat".
+
 ### Updating the SMS server
 
 To pull the latest version of the server code: