MEDICROSS

I am baffled by the fact that I'm sent letters of demand from Medicross KEMBIRCH. Sandra Heine's sent me 2 invoices which show that I haven't paid. I was on discovered Med Aid before I went off. 1 July I took my son and paid cash(500) for Doc consultation and X-rays for 486.00 paid cash. I unfortunately threw the invoices away, but in the emails I attached screenshots of my STD BANK for R500. Then I received another letter of demand for 08 Aug... Which I also paid cash R506, I attached another screenshot and still fail to understand why the apparent R477 I owe Medicross KEMBIRCH is for or the 500. I opened two accounts one for Cash and one for medical aid, and since July and August have only used the cash account. I don't mind paying if I'm in the wrong but Sandra Heunes keeps on sending me the two invoices and I just need clarity what the outstanding amount that I owe is for which consultation because with my screenshots from the bank for July and August I have paid, and the x-ray the person wanted cash.... Can I please have clarity why I'm getting letter of demands and lawyers