Medical bill went to collections- I was not aware of it

Someone just called my spouse looking for me over an outstanding bill from last year. I have figured out, without speaking to anyone myself, that it was a collections agency.

I just did some digging and this was related to a medical procedure I had last year. Insurance paid out their portion, and I know with 100% certainty I never recieved a bill from the provider, nor any notice that I was about to be sent to collections. We check our mail regularly, and we are 100% on top of all bills that come in, especially for medical stuff.

My first plan is to contact my doctor's office when they open tomorrow. Is there any chance of settling with them directly rather than this collections agency?

If that doesn't work, my next plan is to make the agency validate the debt and provide me a breakdown of what they're asking for and why.

Anything else I need to do or consider doing?