Can't claim after 4 months

I got mixed feelings when it comes to making a complain about momentum health. I have been with them for 10 years and they worked fine for me. But something that bothers me is the claims that always come back and bite me after a long time since the hospital admission day. Apparently I owe over 2K for claims I was totally unaware of .got annoying calls from debt collectors saying that I have an outstanding amount for over 120 days when they calling me for the first time. When I research I found that momentum did not process the claims because of pre authorizations and tests delays from pathological services. I spoke to the consultant that visits us at work because 80% of my company people we are on momentum. She explained to me that I won't be able to claim because the claim was not submitted within 4 months. All that information is new to me and I just need to miraculously pay off over 2K from my pocket. Maybe it's me but I really don't understand the point of having a medical aid when you randomly paying huge amounts after hospital visits. I tried to avoid shopping around because I understand every business has its disadvantages but I can't risk my credit score because the service is not user friendly. I'm sorry but you just lost a client