Intermittant Signal & Data after returning from abroad

[longsa]

Hi, 

I returned from France 4 days ago and since then my signal and mobile data have only been working intermittantly. Sometimes my signal is fine and I can make and receive calls, other times I can be on a call and then the other person suddenly can't hear me, or sometimes it won't even connect the call at all. 

Mobile data is the same. I can have 4G in a location and then 5 minutes later the phone is still showing 4G but I have no data signal and whatsapp etc won't connect. 10 minutes later it will work again. 

I have reset network settings which hasn't helped. 

For info, my APN is set as idata.o2.co.uk

Does anyone have any advice?

Thanks 

[MI5]

@longsa 

Start by removing and reinserting your sim if you can.

Next check for any local network issues and see guides:

O2 | Service Status

Guide: How can I sort out my network issues? 

Guide: Is the network down for me or everyone?