Failure to close off a credit card as agreed!!!!!!!!!

My standard bank credit card was handed over to MBD. I received a call from them on the 5th December 2021 and I stated that I wanted to cancel the credit card. The lady said to me my outstanding balance was R377.80. I instructed her to debit my account on the same day with the outstanding amount and close off the credit card. The money was deducted from my account on the 6th December 2021. She stated that she will send me my paid up letter and instruct Standard bank credit card to close off the credit card. To this day no paid up letter has been provided and when you call their call centre, the phone rings unanswered. Can you please assist me with this pathetic customer service from MBD. They are quick to make annoying phone calls, however when they need to execute client's instructions, they fail dismissally.

Desired outcome: proof that my Credit Card has been closed.