The iPhone 7/7 Plus have a signature ic fault similar to the iPhone 6/6 Plus touch ic fault. Due to internal flexing caused by normal daily use(sitting, bending, dropping, etc.), the audio ic connection is broken loose from the logic board. When this occurs, you will experience one or more of the following issues:
Fortunately, this can be repaired by removing the audio ic and attaching a floating jumper to the problematic pad preventing this problem from happening again. Once this is completed, a new audio ic is installed. This is a higher level main logic board repair. Electech has the high level skills and tools required for this repair.