My house buyer can’t get a new account

I’ve told Bulb that we’re moving on 21st July but the buyer is being told that we haven’t

I dont understand your question, have you already moved out? or did you tell Bulb on the 21st that you are moving out at a future date?, in which case the buyers information would be correct.

Best talk to Bulb about this I would have thought, rather than us fellow customers.