Cancelling a PAYG energy and gas contract before its live?

dekaspace

Had a door to door salesman offer to change me over to Utilita, a lot of things he implied I did check and seem to be wrong but one I did not check right was the 14 days to cancel, what I was told was its 14 days from when I get a letter to say switchover would be within the next 28 days.

Anyway I have to move house at the weekend and only just found out so rang up and was told it was 14 days from sign up so could not cancel, but I could cancel if I was moving but said switchover was next Monday(less than 3 weeks after I signed up but longer than 14 days) so wanted to know in this sort of situation since I am moving before its changed over what is the correct thing to do? Because if I phone to cancel due to move does the new tenant just move in and change to new supplier?