Some callers can’t hear me but other can -iphone6

I’m experiencing an issue with callers not being able to hear me when they call. I have tried loud speaker, still the same. Have tried answering via Apple Watch and the caller can still not hear me. Have turned the watch off Incase it is causing an interference but I still experience the same issue.

I reset network settings and tested using Home phone which test successful. But when I called my phone with my other iPhone it failed.

I’m pretty confident that it is a bug in the software. I can record my voice using voice memos.