Q: Whilst making a call the audio is intermittently cutting out, I can't  hear caller and they can't hear me. This will then resolve for a few seconds before cutting off again. When the call is ended it takes about a minute for call to end.

I have an iPhone 6 running on iOS 9.3.3 it is 11 months old.

When making or receiving calls during this last week the calls are intermittently dropping in & out, person on other line can't hear me and I can't hear them this is regardless whether I have made the call or whether I have been called.

When the call becomes audible again after a minute I can continue call only for it then to drop again. When the call is ended it takes around a minute for call to end and then tells me call has failed.

I have tried system reboot countless times, closed down all apps and tested network coverage.

Any ideas, impossible to take or receive any calls at the moment.