I have a 100gb sim card and recently when I was abroad I used up the 12gb allowance within a week just keeping in touch with people and working. This was very inconvenient. Why is there a 12gb limit no matter how much data you pay for in the UK?
I don't know if this helps you at all but when I'm not using my phone directly I put it into Airplane Mode. This shuts off all activity and I can monitor my usage more easily.
