This kind of issue would only happen in GSM gateway.
Call service request failed. Call service is not working after set on Yeastar device.
1. USSD theory. Go to the first chapter to get basic understanding of the function. Call Service Flow
2. GSM trunk registration. Check if your GSM trunk is registered or not.
3. SIM card balance. Check if your SIM card own enough balance.
4. Test SIM card on mobile. Test the call service on the phone.
5. Contact carrier. Contact carrier support to see what happened.
If issue persists after finishing the checklist, please post us the following information via our support portal.
- Problem description.
- Result of each step in the check list.
- Screen capture of call service setting on the GSM trunk page.
- AT Command log. How to Get AT Command Log