Q: iPhone 6: No sound during calls, Apple Repair says device is O.K.?

Hi all,

I am having trouble with my iPhone 6 lately. As soon as someone tries to call me or I try to call someone the Phone gets really slow and I cannot hear anyone over speaker / headphones / etc. Playing and recording voice memos works absoluetly finde, so I hardly think that it is a hardware issue?

I already sent the Phone to Apple but received it back with a letter stating that everything is fine according to their testing standards.

Anyone any ideas on how to fix this problem?

Thanks in advance,

Dom