Call drop

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...

• Turn on Airplane mode, wait for 10-15 secs and turn off airplane mode.
• Restart your iPhone (Restart your iPhone, iPad, or iPod touch - Apple Support)
• Force Restart your iPhone )Force restart iPhone - Apple Support)
• Check you Battery health
• Take the SIM out and Put it back again
• Change you SIM, if it is damaged
• Time to contact your Carrier / Change if required

If you are experiencing call drops consistently, then please check the following...

1. Check your network signal strength: Poor network signal strength can cause call drops. Check your phone's signal strength indicator and try moving to an area with better signal reception.
2. Restart your phone: Restarting your phone can sometimes resolve issues with call drops.
3. Update your phone's software: Make sure that your phone is running the latest version of its software. Go to "Settings" > "General" > "Software Update" to check for and install any available updates.
4. Remove any case or cover: Sometimes, a phone case or cover can interfere with the phone's signal strength. Try removing any case or cover you may be using and see if it resolves the issue.
5. Contact your carrier: If none of the above steps work, it's possible that the issue may be with your carrier's network. Contact your carrier's customer support for assistance.

If the issue persists, you may want to take your phone to a certified repair shop or contact the manufacturer's customer support for further assistance.