Pay who?

Visited the emergency room. The bill was billed to my health insurance company. The insurance company refused to pay (not in the range of the coverage) and wrote a notification to me. On the notification, there is creditor name (an association), but on internet, anyhow I cannot find this association. So I keep waiting the bill from the creditor. But suddently the collection company contacted me for that bill plus interest.

I think that the interest is not my responsibility because I never received the bill. But small amount, I don't really care.

I can pay the collection company to settle this issue. But I hope to directly pay the creditor. Is there difference between them?