When you change tariff with the same supplier, the monthly costs shown on Cheap Energy Club are the amounts you’d be paying on the new tariff if your usage doesn’t change. However, most suppliers don't automatically update your direct debit when you change tariff with it. Whilst you're charged at the new rates of the new tariff, your direct debit won't normally be updated until your next direct debit review (normally every six months).
In the meantime, this may mean you’ll build up some credit in your account with your supplier. However if you don’t want to wait, many allow you to tweak this online or over the phone.
For more information see our Cut Energy Direct Debits guide.