Bank details not changed

I have sent through 4 requests now with a letter from myself and my bank statement asking Fedhealth to change the bank details on our medical aid, because the bank account number they have is incorrect, Nonhlanhla called me asking for a letter, which I emailed through to her, Anton Singh has also gotten this request with the letter and my bank statement to change my bank details, but they just refuse to do their jobs, last month they debited the wrong account no, and my medical aid got suspended, since the 3rd of April, I have been asking them to change the bank account number, they STILL HAVE NOT DONE THIS, now my medical aid will be suspended AGAIN due to INCOMPETANCE. Claims will come through since my husband was in an accident, and if those claims are interrupted because the payment was not recieved Fedhealth will answer to me, because I have been begging them to just do their jobs and change the bank details, what else must I do to get this right