Why can't my partner hear me during calls or FaceTime on iPhone?

I try to call my partner, weather it be phone calls or FaceTimes, she can see me just fine, but she can’t hear me

most of the time. I might be able to get 2 words out before she can’t hear me for another minute or two. It started off something small but it’s been getting worse recently. Idk if this is a problem with my or her phone, or maybe it’s our network carriers, I’m desperate for answers

[Re-Titled by Moderator]