My suggestion is since your extremely new to the game I would avoid buying a character as you literally have no idea how much you don’t know yet about this game and what kind of a character you would need to buy to play in the way you still haven’t figured out yet.
I would take your time with your current account, try out a lot of different things in the game and watch many many more youtube videos but most importantly connect with other players who can quickly tell you what you need to find out about with concern to buying a new character.
You may have gotten flagged for making a PLEX purchase immediately after already making a purchase. Which might make it look like you were stealing a credit card info and did a test purchase before going for the goods. It wouldn’t be because your bank flagged the purchase that would mean the credit card doesn’t work nor the payment go through.
When you get your account back, check your “PLEX vault” for your PLEX as you need to sell it for ISK in game before anything goes into your wallet.
I don’t know what the fraud would be for purchasing a large amount of PLEX as a new player but maybe they we’re worried about credit theft as it would seem odd to make two similar purchases one after another, 20$ the first time and then 500$ and yes a new account would make that suspicious as someone is not going to use their own account to steal someone’s credit info to make a purchase.
Submit a ticket, explain what you think happened or what you know you did and if there is no foul play involved you will get everything back or if it turns out you did steal someone credit information then you are basically ■■■■ out of luck.