@Apola55 First of all, you should be able to refund the Steam version if you haven't launched it and it's been less than 14 days since you bought it.
If you have a teen account, you can buy games from Origin provided that the linked parental account has set a teen spending limit, and of course that the game costs less than the limit. The minimum age for teen accounts differs by country; if you're above the cutoff, you or a parent should be able to "age up" your account.
A child account can't buy content online, but you can buy a Sims 4 pack on another site and register the product code within Origin. This is the only way to add games to child accounts, unfortunately. I don't know where you live, but in the U.S., Newegg is currently selling Sims 4 content at a discount.
I suppose you could also make a new account, if your parents are okay with it.
