Chosen Solution
I replaced the screen on my iPhone X, now when I am talking to someone on the phone, I can barely hear them. I have to use headphones or the speaker phone.
I discovered the problem. I just barely tore the ribbon cable leading to the earpiece.
Sorry to hear this. iPhone X Earpiece Speaker and Front Sensor Assembly Replacement iPhone X Earpiece Speaker and Sensor Assembly
Another likely cause for this problem, for others who are experiencing it: Check the earpiece speaker, and look to see if there is a tiny piece of plastic covering it. Some replacement screens come with this, and it can be hard to see! I went for a whole week thinking I messed up a repair, until I found it :)
