Just want to make people aware that they should not just rely on the data roaming slider to stop roaming charges. I have just got back from jamacia and have incurred roaming charges to the tune of around £30. Before I left I turned off data roaming as I always do when travelling abroad. However on this occasion it wasn't enough. After noticing the charges during the holiday I was advised to turn off mobile data, which I've never had to do before, as well. This seemed to stop the charges. I have an iPhone 6 and it is fully updated. I've also found out that there is history with O2 over this problem in the past. I will be speaking to O2 tomorrow.