Thanks, much appreciated I could see that I had made a mistake but couldn't see how to correct it.

Hi, I am new so this may well have already been covered by someone else.... My partner has been paying an agreed monthy fee to BMS(HLCF) re outstanding laon with Barclays. CCJ was issued back in Sept 2004 in Barclays name, ignored at time but since 2007 have been happily paying with no problem. July 2010 no payment collected so spent the day tracking down debt to a Geoffrey Parker Bourne Ltd who claim they have taken over debt. He naively paid them without any paperwork the o/s monthly amount owed to BMS last Wednesday (Aug 4th). Saturday letter received(dated Aug 6th) saying they have taken over conduct of account and enclose by way of service upon you Notice of Change which has been filed(not stamped or signed) for £4509.22. Letter notes that he pays by way of instalments and wish to maintain current arrangement. This morning get a letter(dated Aug 4th) chasing up £4042.50 saying that they need to speak to him regarding the o/s balance and that if he cant pay full amount immediately may be able to arrange a suitable repayment schedule. If he doesnt call further action may be taken. 1) can they sell a debt on like this? 2) What is legal position, happy to continue paying BMS the monthly amount as agreed via court so not trying to shirk responsibility 3) can new company threaten legal action against him Thanks in advance