Account in arrears after payment was made

The Ackermans head office is failing the customers. Have an account with the store but mu inquiry was never resolved with them. I normally make payments in the store. Forgot to pay for the month of November. I was reminded by sms to make a payment because I was in a good state to go to the mall I was happy to get an sms from Ackermans with their banking details for an EFT payment. Confirmed the Ackermans banking details with their Ackermans home page on the internet , then used my account number as reference. A few days later I was still getting sms that I must make a payment but the sms stipulates not to worry if the payment was made already. Sometime this month am getting an sms of an increased installment. Am very furious because I made an EFT payment but my account is in arrears because my installment has increased. Went to the your store I got helped by a lady who called head office with tracking my payment that I was told was not reflecting on the side. Payment was made on the 4th of December but still not showing on your side after so many days. Used the banking details from the sms that was sent by Ackermans and the details are listed on the internet as well from your site. I was told to send the proof of payment and was given the email address to send to. Now my worry is who is liable for the arrears in my account of which I made payment, am not going to pay for that. Secondly why must I send proof of payment to Ackermans when I used my account number details as reference am sure that can help with picking up the payment was made for which account. Now I took my time trying to fix this by going to your store and head office was contacted and failed me big time. I will send proof of payment to the emails address provided to me but am not going to pay for the arrears from my account as I am making my payments on time to avoid penalties. So upset now that I have to take time and send proof of payments while I was nagged by your sms's to make a payment. After making the payment am now told it's not showing and have to take my time and send proof of payment as if I don't have other things to do. Am never going to pay the extra money Ackermans must deduct those arrears. I honored the sms and made a payment that I have to prove to your company again I did pay. It's very frustrating for such a big company to fail customers like this.