The way it should work is you are billed as per normal up to your disconnection date.
So I am guessing the £64.92 is made up of a charge from 28/11 to 11/12 at your discounted monthly subscrition and 11/12 to 27/12 at the higher subscription rate to make a month at the two different rates.
A few days after you are disconnected you should get a final bill showing the balance on the account. That should be a rebate on your account for the period 11/12 to 27/12 and you should not pay out anything else after 28/11 once the final bill is generated.
Naturally VM likes to hang onto your money for as long as possible before returning it to you! If VM wants any kit back, you should return that as soon as possible to avoid any charges against unreturned kit.
VM seems to return credits in the form of a cheque. I think I have read on here that if the direct debit is still in place the money can be returned via that (but I don't know if that is a fact or not). When I left VM I owed a small amount of £4.33. I left my direct debit in place and that final amount went out by direct debit on the final billing direct debit date after disconnection.