Being chased for a "non persuable debt"

[Caneluna]

I had a debt in 2007 with HSBC of £1700 which they agreeded and put in writing to me that they would longer persue (due to my disabilty, medical condition and finacial situation).

I have now been contacted by MKRR, a debt collection agency, who claim that they have been sold the debt and are asking me for payment.

Where do i stand on this and what if anything should I do?

[MASS1961]

Debt collection agencies are a real pain. They have no power but will keep pestering you. Do not acknowledge them. You have NO link to them and should ignore them. More fool them for buying the original debt from HSBC. They will probably try other tactics, just keep ignoring them.
If necessary contact a solicitor with your letter from HSBC.