Harassed by Ampath's debt collectors for disputed claim

This matter has a long history but I will keep it brief. I spent months trying to get to the bottom of an amount claimed by Ampath relating to my daughter's stay in hospital. I eventually figured out it was an amount initially paid by medical aid only to be reversed months later. Ampath simply went ahead and handed me over to their debt collecters who claimed payment without providing any supporting documentation. I contested this with Ampath for a long time before giving up and just paying. Now Vericred is demanding payment of collection fees. I refused to pay Vericred and have been trying to lodge a complaint with both Ampath and Vericred, but they are simply ignoring any communication I send them. I have specifically asked their staff to provide me with formal complaints procedure, and this request too has been ignored. I find this to be unprofessional and dare I say it pathetic conduct.