Game really dont have a clue

I had settled my account with Game in September 2018. To date, on a monthly basis, I get reminders to pay my account which is in arrears and to date, on a monthly basis, I have to call them to remind them that my account is fully paid up. When they log on to the system they can then see that my account is paid up and apologise for the inconvenience. But alas, every month, the same thing happens. I have now been asked to supply them with a settlement letter as proof which I did not receive EVER. Although they can clearly see on their system that this has been settled IN FULL. I called AGAIN yesterday to now close my account and to date, I have not received any confirmation that this has occurred ONLY A REMINDER TO PAY MY OUTSTANDING AMOUNT!!!! The worst retail outlet ever! Game, please sort your left and right hand problem out immediately!