No sound input on iPhone 7

Hey everyone!

I have a very strange scenario in my hands..

My iPhone 7 currently running on iOS 11.2.1 suddenly stopped being able to receive any audio input.. For example, no audio notes can be made, can't record any videos, take any live photos, can't use Siri, and then when it comes to phone calls it's even more strange; if I receive a phone call and answer it normally or while connected to Bluetooth earphones, neither party can hear anything. The same goes for making a call without Bluetooth earphones.. However, if I make a phone call with Bluetooth earphones - works flawlessly. Same goes for making audio notes whilst connected to Bluetooth earphones. I have not checked if I will be able take videos whilst connected, but can't imagine it to be information of utmost importance.

I have taken my phone into numerous iStores, all of which the floor and tech support have had no idea what the problem is. I have tried updating, restoring from iCloud, iTunes, the whole toot with no luck.

If things are strange enough, I am unable to restart my phone.. Successfully anyway.. Upon restarting my phone, it immediately goes into a never ending boot-loop. This happens every time without fail. And it doesn't right except for one method.. Sticking my phone in the fridge.. And of course, this too fixes it every time, without fail. So it obviously also has something to do with the phone getting too hot. I have noticed this upon just everyday use where my phone will become incredibly hot in doing the least CPU demanding processes.

So I have no idea whether these two problems are somehow linked or whether I truly got a 'bad Apple', but either way, I am being told that sending my phone away for repairs is the only thing I can do, but I use an Apple Watch so would mean that wearing it would become somewhat redundant for the next two weeks, so this really is something I would like to avoid if possible.

Any help, suggestions or comments would be really appreciated!