O2 - Awful call quality. Mutes intermittently & sounds underwater.

[MI5 Level 94: Supreme]

Download this app to report the issue https://www.o2.co.uk/apps/my-network

[KarinK]

O2 say nothing they can do so have to go elsewhere.
Great! Been an O2 customer for 15 years!

[jonsie Level 93: Majestic]

Best option to be honest. Try some free other network sim cards in your phone. I wouldn't be struggling with O2 if they can't help sort their network out in your dstrict.