Full signal, however calls fail, texts come through in groups

Friend of mine brought his 5c to look at. signal shows fine all the time. however calls to and from fail. texts come through in groups. can also send texts but sometimes fail. tried changing the caller id setting. everytime I check it it's gone back to disabled? it got wet in his pocket when it threw it down last week however no visable signs of water damage. the internal sticker has gone pink so would appear some moisture could have got in I guess but strange as texts do come through. gave it a clean with isopropyl. however not removed the plate to the components under the sim on the logic board as wanted to exhaust all other options before cutting it off. any ideas?

Jay