Bad service @ Hilton Life Hospital accounts department

Out of the blue, I receive emails of Final Demands threatening to hand me over for a shortfall on the acc, which I was not even aware of until receiving these Final Demands. Upon investigation, it turns out that med aid is at fault. So I have emailed back on more than one occasion with zero acknowledgment. I have tried calling more times than I care to count, either it rings endlessly until it eventually rings off, or my best yet... listening to the automated voice telling me "your call will be answered shortly" for over 15 min (on my cell phone!! ) only for the call to be picked up & immediately put down. I've left msgs when the automated voice prompts me, but to date no one has called back, I have even called Head Office and had no luck getting thru to anyone there either. I've also completed the online form. And still I continually receive these threatening Final Demands from Hilton Life Hospital accounts department. What is a person to do to get thru to them? Go to Carte Blanche? ...... THEIR SERVICE IS APPALLING!!!