Confidentiality breach and non-payment of refund

Lancet sent me an invoice including a charge of R850 for a Covid test. I paid the full invoice. Discovery then sent me a statement showing that THEY had paid for the Covid test. I emailed Lancet regarding the double payment on 11 May. I finally got a reply on 17 May saying they’ll look into it and have still not heard anything further. I have phoned the call centre and the agent who assisted me agreed I’m due a refund from Lancet but couldn’t get through to the refunds department. You send threatening messages when a payment due to you is late (in fact, a past payment wasn’t even late but hadn’t been captured by your accounts department) but you yourself don’t make timeous payments! Further to this, Lancet keeps sending my invoices to my father, when I haven’t been on his medical aid for 8 years! I have updated my details countless times and yet my documents still keep getting sent to my father. THIS IS A MASSIVE BREACH OF PATIENT CONFIDENTIALITY! I want my refund to be dealt with immediately and my updated details captured once and for all!