Lancet want quick payments,but NO customer service

I had blood tests done on 29 April 2021. I could choose which lab the blood test should be sent to ( sadly I choose the poorest lab) i got a bill a few days later. They expected payment in 7 days, which I made. ( I later found out they over charged me with plus minus R1400,now my account is in a credit) I paid EFT and wanted to see if my medical aid would pay some of the tests back to me. I submitted the invoice and proof of payment to Discovery, only to find out a few days later that Lancet did not use the correct GP practice number and not the correct ICD10 codes. The agent on the phone from Discovery phoned Lancet directly and I was told Lancet with submit and undated invoice to Discovery. A week later I phoned Disovery to hear the progress of the claim,they say Lancet STILL did not submitt the corrected invoice. Another call to Lancet I was told they will sumitt the invoice to Discovery. I sent two e-mail to Lancet requesting they send me the updated invoice so I can submitt to Discovery. They did not even bother replying. Another call to Discovery,still no updated invoice was sent to them. I phoned Lancet AGAIN, where I was placed on hold and then cut off. Another call, all of this to a JHB number!!!! My airtime and time during working hours to sort this out. The guy at Lancet said he will send it directly to me,but STILL nothing. So where does this leave me? Why is it so difficult for them to send me the correct invoice with the correct dr practice number, they stuffed up,so now I must 'suffer'. That is really bad customer service Lancet!!!