Can get account closure letter

I have settled and requested my account closure letter since 28th July, its been a month since requesting my account closure letter, constantly getting a response from a new person never the same, not getting anywhere. But receiving sales calls, wanting me to sign up. I have had terrible service, they cant provide me with a time frame of when I will get my account closure letter. If my account gets debited AGAIN as they have been and I'm currently in a credit with them. Then I'm posting all my mails and theirs and contacting their ambutsman