Bad servise

I made an online payment in March towards my Markham account due to lockdown and stores being closed. To my amazement the payment was never credited to my account, when stores opened I followed up and was advised that this would be amended as there was a backlog due to lockdown, however we are now approaching October and nothing has been done. I have made countless trips to the stores, sent emails and also made calls to the contact Centre, at my own expense! I need this to be resolved asap as I don't delay in my payments and if that were the case the retailer wouldn't have this much patience. The level of incompetence is appalling