Figma subscription issue

I have used figma's free plan for a while, and then upgraded it for convenience (just to be able to remove backgrounds from pictures really) - I paid for the most basic plan they have, I believe? It was 40$ for annual subscription, and it was very convenient for a while. I paid it in February, and today, they have charged me for monthly subscription which was 171$???? I have not upgraded my plan, nor have I changed it from annual to monthly. Maybe I did something wrong, but idk... I am very confused, because I'm not well-versed in design apps, so any help or advice is appreciated :(