Disappearing Data

<br> I'm back again with the same complaint of disappearing data. A new month and instead of a total of 4GiG on my iPad I only have 2GiG. I would like to know what has happened to the other 2GiG? I should always start the new month 4GiG because of what is carried over. This month nothing was carried over.<br> My mobile data is always switched off, I check my balance before turning it on and using it. And today when I went on to the app to confirm the balance which should have been 4GiG the balance is only 2GiG. Last day of last month I didn't use it but I checked and it just under 4GiG. So what has happened to the unused 2GiG that gets rolled over? This once again about the 072 number on my contract, which is not the same as my mobile number which is the 082 number.