I spend a lot of time in Hungary and frequently my mobile data stops working.
As it was working I know that this is NOT a setting issue on my iPhone.
The solution is to ring O2 support (+44 7860 980 202 but please check this yourself in case O2 change it) and explain that your mobile data was working and stopped.
It stops when a billing date occurs for some weird reason. I logged in to MyO2 and had used practically none of my data allowance.
Every time it happened in the past I was told that they had to tick a box that I had an iPhone on this number but today I was told that he reset my data.
I had to power reset my device and the data worked immediately, although I was told that it could take up to 4 hours.
Thank you for fixing it so quickly O2. Shame it is not a permanent fix.
