Data rolling being taken back by sky

[PhDo80]

My wife and I had built up a data pit of over 1TB. We used bits each month to cover us on a lower package as we had such a good deal when we first joined sky. Now they have recently just taken over 1000gb back. However, in there terms and conditions it says after a year we will take back each months data that has been unused. But they haven't done that they've just taken it all in one go. 
Any ideas? 

[TimmyBGood]

@PhDo80 

After a change in T&C's unused data now expires on a rolling basis 12 months after being added to the Piggybank, but the accumulated lump older than one year at the date this change was implemented would evaporate all at once.