iPhone 7/Plus Unclear sound to others during a phone call

[TWDbag]

Hi,

Recently I am experiencing some phone call issues with my microphone, I sound unclear to others during a phone call.
Now, I sound clear while a Viber, WhatsApp, Facebook Messenger calls or any other 3rd party app that supports call via internet.
I sound very clear on Voice Memos, Videos/Camera as well, and Siri can take my commands without any issue, no matter how far away my phone is (reasonable distance).
I don't have any screen protector, films, or case that covers the microphone or iPhone receiver, and microphones and iPhone receiver are clean.

However, I started experiencing this issue after updating my iPhone to iOS 13.2 and after I took couple of phone calls while connected to a cheap speaker via Bluetooth and that very same speaker has a mic built-in.

Can it be something with the software which can be resolved with backup and restore or simply restoring the phone on default and setting it up as a "New iPhone"?
I don't want to rush to the service because in my country we only have an Authorized Apple Reseller, and they say if there is something wrong with the microphone they must change the entire screen (which I think is weird).

 

[akash.nu]

Lots of people have mentioned to me that they don’t hear me clearly on the AirPods anymore. I was thinking this might be down to the AirPods but it might just be the Bluetooth stack. ¯\_(ツ)_/¯

 

[TWDbag]

I just talked with Apple Support (via chat) and we tried couple of things:

1. Reset Network Settings
2. Reset All Settings
3. Turn off Bluetooth

And all of these things didn't solve the issue.

Now they asked me to check if it's going to solve the issue with restoring the iPhone and setting it up as a new iPhone, suspecting it's some software glitch.
I will let you know the results.

 

[akash.nu]

I just talked with Apple Support (via chat) and we tried couple of things:

1. Reset Network Settings
2. Reset All Settings
3. Turn off Bluetooth

And all of these things didn't solve the issue.

Now they asked me to check if it's going to solve the issue with restoring the iPhone and setting it up as a new iPhone, suspecting it's some software glitch.
I will let you know the results.

Those steps are pointless. They’re just going through scripts. Let’s see if restore works for you. My gut feeling is that it won’t fix the issue.

 

[TWDbag]

Any idea what it might be?
Considering it didn't fell nor once before.