Does it even help to complain

I closed my account with FNB in August this year, reason the level of service being so bad. I confirmed that the account is closed, received an e-mail from them(see the e-mail below) AND then today I get a sms saying I am in arrears with my payment. <br> <br> Not only is this exceedingly bad service it also affect my credit rating !!!<br> <br> FNB YOUR SERVICE IS NOTHING BUT RIDICULOUS !!!<br> <br> FNB CREDIT CARD - 4*** 6*** 7*** <br> <br> <br> We confirm receipt of your request to cancel your FNB CREDIT CARD. <br> <br> Your account reflects a credit balance of R85.56 We hereby request that you supply us with your banking details in order for the funds to be transferred, <br> Kindly provide us with proof of your banking details, to the below mentioned fax number, and should you have any queries contact the undersigned. <br> Should you have any further queries, please feel free to contact us on ***.<br> <br>