False Claim

I used Er24 services December 2014. I received a letter from Nudebt 16/02/2016 that I am owing er24 R1562.90. I contacted ER24 to find out they said it is a short payment from my medical aid Gems. I phoned Gems to inquire they said the ER24 claim was paid in full they also sent me a proof of which I forwarded to ER24 however ER24 insisted that the balance was from the short payment they sent me an invoice with the amount being different from the amount claimed to Gems. I asked them why the invoice sent to me is different to the one claimed to my medical aid, no clarity instead they say their rates and that of Gems do differ of which I do not have a problem however when there is a shortage my medical aid do clarify that for e.g amount claimed was R5000 scheme paid R4000 I need to pay supplier R1000 of which in this case is not evident, what the supplier claimed is paid in full. ER24 says Gems has changed their claim. I have proof of statement from Gems that shows what was claimed. They are not willing to show me what they have claimed and feedback that they received from Gems stating that they have reduced their claim. Please assist me follow up with ER24.