Is volume connected to network issues

Network problems generally cause sound to cut out completely rather than just being reduced.

It's not clear from your question which volume you're talking about; is it related to how loud your voice is to other people, or that you can't hear them well when other people are talking on a call? In the former case, it may be an issue with the lower microphone, and the latter would be a problem with the earpiece speaker. Either one can get clogged with pocket lint or debris and cause problems, so you could try cleaning them if that's the case.

Please clarify your question and we'll see if there are specific things we can suggest so you can fix the issue.