I have a major issue with my HTC One, I cannot connect to the O2 network. I have had this problem since I returned from South Africa to the UK. I unlocked the SIM when over there to use a SA sim and then when I got back I could not use voice or text only data on the O2 network.
I searched for a while to see if I could fix the problem but to no avail. So I decided to install the Google Play Edition to the phone (via fastboot), now this is complete with OTA updates and this is now to 4.4 KitKat.
I am not sure what is the issue with it as it will not connect to voice, sms or data now. Could it be the radio? I have changed the setting from LTE to 3G as I dont have LTE (4G).
At the moment the phone is only good as a substitute device when on WIFI...... Help...