Demanding payment for something already paid for

Without prejudice. I was hospitalized, and was sent for a Bone Densitometry. I was told that my medical aid would not pay for it. With severe pneumonia and 3 organ shut downs I had to get out the bed I was wheeled in and go to my ward get my wallet and bring my credit card to pay. Which I did. I have been hounded for payment for that same procedure since 2017. Early this year I had telephonic confirmation that I had indeed made a payment so similar to the amount being asked for that they would get back to me with feedback because it made no sense. No feedback. I continuously get asked for an amount that I have paid for! I tried to reply to their statement email and it bounces back. Net Care refuses to give National Radiology' email address let alone for accounts department. I called NRS and eventually got an email address to which I was to send my proof of payment which is a credit card statement from my bank. I sent said email through giving one business day to respond and put this payment debacle to rest. I have now allowed the holidays and a few other days to pass and have not even had acknowledgement of email. Simple professionalism. In my opinion hounding someone for an amount already paid for, and continuously sending a statement that does NOT REFLECT MY PAYMENT is extortion. The email address I was given was by email so must be correct and is as follows lindsayxrays@nrsmail.co.za and is supposed to be a manager of relevant person. Shocking service from the point of "care" in hospital that I and my drip must go get my credit card to ignoring proof of payment and not even showing my payment received on my statement. Poor accounting. However my opinin