People hear me bad on the phone

Hello, since I changed my battery on my iPhone XS following the tutorial on ifixit, people can't hear well on the phone.

At first, I thought it was the microphones. However, when I tested each one separately with the Auphonic application, I realized that they were working normally.

I then thought the problem lay with the network. But when I tried it out with a SIM card from another operator (I tested Orange, whereas I'm with Prixtel, the SFR network), I realized that it wasn't that, because people still hear me badly even after changing SIM cards. As far as the network is concerned, to be precise: I can hear the people I speak to very well, I've never had any problem with that. The only problem is that they can't hear me. So I'd be surprised if it was the network coverage that was faulty, or the connection to the telephone server.

Taking a step back, I'm thinking that maybe it's my phone's ability to send my voice over the telephone network that's failing (I hope I'm making myself clear...). Or, given that I was only able to test the microphones separately, maybe it's the combination of several of them during calls that's faulty... but if that's what it was, whatsapp calls wouldn't work, would they?

Anyway. I confess I don't know what to make of it. It's still quite problematic for me.

Do you have any ideas on how to solve this problem?

Thank you for your attention.