Account closed but still getting a statement

I closed my RCS account mid 2018 and I received a closure letter. However, I am still receiving a statement for this account. Please close my account PERMANENTLY, I do not want it open and remove my details from your system so that I do not receive any statements from you. I have been trying to call RCS for the past 4 months and I simply cannot get through. You are put on hold for a good 30 min. I am kindly asking that my matter be resolved urgently please. I also suggest you open customer service offices in main cities because you not being unreachable like this is not good for your ratings. You also do not reply to emails, it's frustrating really