The problem is, you have an photo of a box. Which you could've copied from internet or whatever. Or even bought the game second hand from someone else.
So you need to proof that you own the game, normally you would do that with an receipt of the store where you bought it.
If you don't have that, it's getting harder and harder to proof. You could check if you paid for the game with something else than cash, and look up the date and time you bought the game.
After that you could contact Big W to ask them if they can send you that receipt as you need it to proof you own the game.
If you have found that, make a picture with all the information EA needs to confirm you bought this game legally, and it's yours.
I understand your frustration fully, sadly this world has a lot of people that can't afford or aren't willing to pay for games and try to rip off companies like EA on a daily basis.
EA can't see if the person using your code got it legally or not, so they can't just take their code out of their account.