American Medical Response Differing amounts owed Bay Area Credit Serivces Internet

Bay Area Credit services contacted me on behalf of American Medical Response. They hadn't contacted my insurance for payment on an ambulance ride. They were harrassing me at work. 

They finally received payment from insurance and I owed them a balance of $180. I paid $40 and then $10 and I continued to hear from Bay Area Credit telling me that I hadn't paid anything.

Bay Area Credit called me at work and told me I owed $220 immediately. I told them that I'd never owed that initially. They told me 'interest was accruing'. What?!  I had just received a statement from American Medical Response saying that I owed $130. When I told them that, they said 'You're lying!'.

I called American Medical Response and they told me they had a record of $130 and that was it.

I paid the balance and demanded that they call Bay Area Credit and told them never to call me again.