Account Sent To Debt Collectors Instead Of Blocked

I reported my card ****** last year December and specifically asked if they could block my card. It was confirmed that it was blocked. This was reported In December and ever since I have been battling with Mr Price's in-store staff and staff at your accounts departments to pay my monthly instalments that were due. After numerous attempts and being reassured that my account could not be found/did not exist I gave up trying. This was in March 2015 that I decided that I will not continue to waste my time and put all this effort to pay my account that cannot be found. I have never been called or informed that my account was in arrears nor was I informed that my account was handed over to a debt collection agency. It was only when I tried to apply for a home loan that I was informed I'm in arrears for my MR Price account. When I tried to settle this account for a settlement letter I needed for the bank, Mr Price informed that my account was sent to the collection agency. So instead of blocking my account Mr Price sent it to a collection agency where they waited for my instalments to pile up and now expect me to pay a lump sum to receive this letter!