Has this ever happened to anyone...?

I was checking my account online and thought my balance didn't seem right. So I looked at recent activity and there was a rather large transaction posted to my account yesterday that I hadn't made.

The merchant (or whatever) was a website I didn't recognize. I went to that site and it was a place that handles payments for other places. I think it's French because some of the instructions were in French as well as English. And the English was very poorly written in some areas.

By providing certain information, I was able to get all the particulars of the transaction. I thought it was funny because it said "look at the merchant below to see if you were the one who made the transaction".

Anyway, I had never heard of the merchant. There was a "LTD" at the end of the name which leads me to believe they're British maybe? I supposedly made the transaction on 2/9 but it didn't post to my account until 2/18 (that's odd to me...9 days?)

Unless I'm having serious memory problems, I didn't make this charge. But I don't know how to handle it. Well, obviously, I'm going to call the credit card company but will they believe me? I don't have any experience with this kind of thing. How did it even happen?

I've used an NROP recently. I wonder if someone there took my info and charged something. Is that possible?

If anyone has had any experience with a situation like this or can offer me any advice, I'd really appreciate it.

TIA!

Imago