Inform the Collection Agency that the matter is in dispute with the supplier (NTL) and that will put a pause on their steps to recover the money.
If you are willing, call them and register a complaint. This is a usual first step, and should get the situation reviewed. Don't simply accept the person looking into it, get them to record it as a complaint.
Following that, write to NTL detailing:
- The contact your wife had with them
- Why the £5 was adjusted on the bill
- The fact they dealt with your wife, not you
- The failure to mention any tie in period/send you any documentation dealing with it
- Include any reference number given when you complained on the phone
- Then outline the cancellation was in line with you having had the service for 6 years and being outside of any minimum contractual period.
- That you want confirmation that no outstanding sum is due
In the letter give them 14 days to respond to your letter, and if they haven't replied within that time, send another letter referencing the first (and including it if you like) giving them a further 7 days to respond. Usually by this point they'll have sent something back - or decided it isn't worth the hassle of pursuing (possible if they still think they are right, but have a weak case/procedural defects in the renewal).
If you really want to put them on edge, you can also send them a 'Subject Access Request' referring the the recording of the calls between you and them over the specified time period, any letters they have sent (if any) etc. Template is here:
http://www.ico.gov.uk/for_the_public...cess_info.aspx or search google for 'subject access request letter' and it is the top result in .doc format. There is a fee to be paid and you have to wait up to 40 days for their response, so send this separately to the letter outlined above.
Hope this helps