Never really use mobile data but looking at getting something so I can check mails etc when power is out. I'm looking at 'pay as you go', but after browsing around it seems no matter what data I get, it will expire at the end of the month. I recall seeing stuff about this a while back, does it still expire at end of month? e.g, if I buy 100mb on 29th will it expire on 30th, or will it be 30days from the date I purchased it i.e. 29th of following month?