O2

Why after a year of a two year contract with O2 (for I pad) am I getting messages half way through my billing period telling me I am out of data? I use my I pad for looking at my e-mails, face book and reading/sending messages, I am elderly and am do...

I have 2 x O2 sim card and have muddled them up how do I find out which sim belongs to which device one is from i pad other from i phone each on a diffrent tarrif?