Having the exact same problem and the man at Vodafone store told me about the calls sounding like they are under water before I had a chance to tell him too as he has at least 20 people each day with that same problem. I have had this problem for over a month now. When you ring them they pretend to have not heard of the problem! It's like they have had special training for this, they will try all sorts of delaying tactics with lots of trouble shooting things to try. I've done them all, deleting cache memory, tried different sims, turned off Wi-Fi calling, full factory reset and even got a brand new replacement s7 edge yesterday. I still have the same problem. The problem is not with the phone it is with Vodaphones s7 android update so only they can fix it. I've looked on line and seen that it's affecting people in Germany too so the problem must be massive hence them not acknowledging it for fear of losing so much customers and money.
We need to let Samsung be aware that Vodafone are forcing customers to look at other brands just to be able to make calls.
Hit your social media and spread the word, as I'm doing
