https://www.bt.com/help/account-and-billing/manage-account/thinking-of-leaving-bt
if someone left a few days before the actual expiration of the minimum term , or a few days after ( and therefore pay a few days at the higher out of contract price , those few days are likely to be a very small amount of ££, a more important thing to consider is the billing period is not likely to coincide with the date notice is served, or the date of leaving, so chances are the next full month will be paid , and the days charged for after the cessation are refunded, so don’t cancel the direct debit …..trying to leave on an exact date is not always possible but it’s hardly worth stressing over a day or two either side of the date you want , but obviously to make the last month of the minimum term and the 30 day notice to be the same period call as close to a month before the expiry of the minimum term .
