Change Of Decoder Ownership

Could you please advise how long does the change take once the forms are sent through? I called your call centre and they don't seem to know either. I was advised by them that I should just submit the forms. When asked if the current subscription will be cancelled, they said yes. They could not give me details or what happens when the change is done. Please advise as I need the change to be done to the new owner before my next payment is due. Thank you.