Terrible treatment from Ampath

Ampath have been calling me since last year to pay an outstanding amount. I have been calling them back and asking for an invoice to make payment. I finally received the first and only invoice on the 10 May and made payment 5 days later, and sent through proof of payments 4 times without any response. Only to find that Ampath handed me over to a third party collections company which was asking for almost twice the initial cost. When VeriCred called I confirmed that I had made payment, I even sent them the proof. However I am still harrased until today from them and still have no response from Ampath. Ampath as a company have terrible admin processes and even worse customer care. I wish these hospitals can stop using Ampath.