@janmon: It's difficult for me to determine from this position. To troubleshoot the issue, try disabling VoLTE, or turning off your mobile data next time you make a call to a friend on the O2 network from your home. If the problem is only occurring at your house, and your calls are unaffected elsewhere, then this suggests that there is a potential O2 signal issue in your area. With this in mind you may wish to reach out to O2 directly to enquire about any problems with the service at your address, or in the surrounding area.
