They text me at 80% and then it went with in an hour or so.
I was putting a new ROM on my phone and I think that used most of it.
I've asked the same and they said no.
On my contract they give me credit to use on phone calls and text. Its something like £190 a month, I've used almost £10 of that, I asked if I can spend the excess on internet boosters (I got two weeks till I get my 3 gb back) and they said no.
I'm also due an upgrade and they wont give me the HTC One for free, so I'm looking at going Sim only and getting the Nexus 5.