Default My Nightmare Z1 (calls not working)

So back in January the 10th I made the mistake of buying my lovely Sony Xperia Z1, and as soon as I took it out of the box and started calling people I started getting told that they couldn't understand what the hell I was saying. I was really happy with my phone otherwise, and didn't want to turn in the phone. So I waited for the 4.4 update hoping it would fix it. I waited for quite some time, because every time I checked it was just one week away from release or something like that.

Anyways, when the phone finally got released, it didn't fix a thing, (and made the notification pull down menu ugly as hell, lol)
So I turned my phone in for repairs. About 2 weeks later it was returned to me, no problems found. And I got it back in the same condition, just factory reset. Wonderful.

So I went back with it again, explaining it in further detail, that it was sporadic, only sometimes would my calls become really choppy, and nobody would be able to understand me. So we wrote a much more detailed report on what is wrong with the phone, explaining everything.

Once again I get it back, no errors found, but factory reset. Only now the camera locks up every time I take a picture, and the power off button won't work, the wifi is slow as hell, cant watch videos, streams, anything. And I keep losing the signal.

Anyways, I've turned the device in now for the third time, but I have a feeling itll get returned still broken as hell, or even more broken somehow.

I talked to the guy at the shop, and he said they couldn't give me a new phone, even a new z1, either, if thhey don't find an error.

In the beginning the guys at the place I bought the phone thought it was because of the place I lived (a mountain village in the middle of nowhere)

But now I've moved across norway into a pretty big city, and same issues wherever I go

So now I'm at the end of my ropes, I'm starting to think I should just leave it in my car as a GPS and keep using my nexus 4. That or tape it to my toilet and use it as a doo doo target.