I have managed to fix The G4, after reading around on the web, there are dozens of forums and help pages having this problem on many different phones, all using Lollipop, dont do what I did and Panic post a huge mess of a forum thread.. Oops .. its a simple App conflict, not a faulty phone:
I know lollipop is dying off now, but heres how i sorted it:
- Even though my G4 is branded to EE, its SIM unlocked, so I put a different SIM card in... and after about 4 minutes, it detected it, so this may have fixed the "Dialer" cache.
- A second solution, which worked also on the S5, is to goto "Settings" > "General" > open "Apps" > slide along to "ALL" tab, scroll down and Clear Cache, Clear Data of "CALL" and the ones listed "PHONE".
Restart the phone, this should fix it.
Hope that helps anyone else