Jet reluctant to admit that account is paid in full

I have paid off my account for Jet Stores on 6 September 2019 and the account is now closed. . I have contacted MBD Credit Solutions again asking for a letter stating that the account is closed. I also phoned Jet stores who told me that the account is closed but I must phone Jet Customer Service to ask for a letter stating that the account is paid in full. Jet Customer Services told me to scan my last payment and send it to them because after a month, the payment still does not reflect on their system. It looks to me that Jet and MBD Credit Solutions are both reluctant to admit that the account is paid off. Two different departments at Jet Stores give me different information on this account. In the mean time they will again find that I owe more money because they are not able and do not want to close the account. This is unfair. I received phone call after phone call when I still owed money on the account. Now that the account is paid in full, they do not want to acknowledge that I do not owe them anything.