Turn Airplane Mode on and off. Go to Settings and turn on Airplane Mode, wait five seconds, then turn it off. · Check Do Not Disturb. ·
If you can't make or receive calls on your iPhone - Apple Support
This seems like a carrier issue either at your end or the other end.
It is my experince that some Carriers apply priority filters to connect to preferred customers and Carriers depending on which Carriers are on good terms with them.
Please Contact your Carrier (Cellular Service Provider). The agency who issued the SIM to you and to your some contacts. I would suggest you to lodge a written complaint.
This seems surely like a carrier issue. You need to contact your Carrier (Cellular Service Provider), the agency who issued the SIM to you.
Call Failed or Dropped Calls / Disconnecting
In telecommunications, a dropped-call / Auto Disconnecting Calls / Call-Failed Muted conversation are mainly due to technical reasons / fault at the carrier's end. At times the calls are cut off before the speaking parties had finished their conversation and before one of them had hung up (dropped calls or Call Failed or Auto Disconnection or muted calls).
Few Reasons Your device Keeps Muting / Dropping / Disconnecting Calls or encounter Call Failed.
- Your Signal Is Weak.
- It's Raining (Cats & Dog)
- The Cell Tower Is Overloaded / Heavy Traffic (Telecommunication)
- You've Misunderstood Your Signal Strength
- You are moving and the signal weakens while changing from one tower to another
Options Are...
