If you don't know (or maybe the people you've talked to are too polite to tell you lol) some people are experiencing caller echo on voice calls. Usually the person who is talking to you on the phone hears their own voice echoing back to them, as if you were on a bad cellular connection.
I have got around the issue (somewhat) by using the speakerphone, but obviously that's not a viable longterm fix. I believe if you use a bluetooth headset you can also get around this bug.
Anyone else experiencing this, and if so does anyone know of any work-arounds we could try? Maybe from the play store, or something that's worked on another device?