It doesnt have to be an account. It can also be...
You dont know how the seller purchased your code you are buying. If the code you bought was purchased by stolen credit card. EA flags that account and you lose access. When it is reported as stolen.
Dont ever use G2A.com to purchased games or codes. Its a Risk for a ban. Purchase the game using official means of purchase not 3rd party purchases. They might have illegally obtained the code you bought.
There are post all over Reddit about it.
You say your knowledgeable yet didnt have the knowledge to purchase a game the official way. You used a method to buy the game cheaters use. Which is very suspicious to me. I dont care if your friends say you dont cheat. I dont trust any of them either.