@Inversed1 The Sims 4 base game is eligible for EA's great game guarantee, but packs are considered DLC and are not covered. You can read the entire statement here:
https://help.ea.com/en-us/help/account/returns-and-cancellations/
There are times when you can get a refund for a bundle of the base game and some packs, but that isn't always possible; it probably depends in part on the circumstances of the purchase. Additionally, refunds are only offered within 14 days of purchase, and additionally within 24 hours of the first launch, if they've been launched at all.
If you want to see whether you can get a refund anyway, contact EA customer support and ask directly. But don't count on it working out. In this case, unfortunately, you may be out of luck.
https://help.ea.com/en/contact-us/