V confused about statement for supposedly free thing?

I’m new to the US and trying to get my head around everything.

I had an appointment for a well-woman check on 22nd August (which is apparently fully covered by insurance, was my understanding), and I had some tests as part of it.

I think the tests came through on my insurance portal as the original charge being $620.73 and me owing $30.59. I paid it through the portal and I’ve not heard anything to the contrary.

Now I see that I have a statement from the provider I went to for the well-woman check, it looks like $2268.65 is paid for by insurance, and it says I owe $359.23.

A few questions:

This was a well-woman check that was apparently fully covered by my insurance. I actually checked when I was there that it would be covered. Yet this is the largest amount I have had to pay for myself — and I am going thru a couple of medical issues, and have met my deductible. It doesn’t make sense to me to be this much?

This doesn’t appear to have shown up on my insurance portal AT ALL. Which is strange because normally claims go through there within a week and this was some weeks ago now… Do some health providers only process claims once a month?

I feel a bit like I am going mad, is this a normal thing? Who do I speak to to rectify it? I feel like I was told this thing was free and now it’s like “pay us money” but I literally would not have done it if it wasn’t free!!!