People can’t hear me the first 15s of a call

I’ve had this problem for a while now and i can’t find out how to fix it.

Every time i get a call and answer, the caller cannot hear me for the first few seconds. Sometimes its the first 5, sometimes 10 and sometimes even 15. I never know how long it is going to take and i have to repeat ”hello” until they hear me.

What can i do? I have restared my iPhone, i have updated iOS, nothing works.