Game Pass Ultimate subscription not letting me get my money back for gold subscription

If you want to go back to gold, then just turn off auto-renew on your game pass ultimate subscription, and let the subscription run out. Then get gold. If you cancel Ultimate now, you will lose access to the gold that is included with Ultimate.

The Gold would have actually been upgraded to Ultimate as well. So if you bought 1 month of Ultimate, you should noticed you actually have 2 months now. You can verify the expiration date at http://account.microsoft.com

Game pass ultimate includes gold and the game pass subscription so if you have the gold and purchase the ultimate subscription it will cancel the gold subscription and put it in with the ultimate. The Gold subscription will show as being cancelled in your
subscriptions.

If you add a prepaid Gold or Game Pass card while you have a Game Pass Ultimate subscription, the Gold/Game Pass is converted to Game Pass Ultimate at a conversion rate based on the price of the subscription, not the time 12 months of Gold is equal to
the price of 4 months of Game Pass Ultimate. In order to add a prepaid Gold (or Game Pass) and get the full time, you would need to either cancel your Ultimate subscription or wait for it to run out and then add the code after the Ultimate subscription has
ended.

You can't convert it to Game Pass directly.

If you however have an active Game Pass ULTIMATE subscription (that combines Gold and Game Pass), the Gold membership card will add time to your Ultimate Membership.

However, since ULTIMATE combines two subscriptions, you won't get the full 3 months from the "Gold only" membership card.

According to the
Game Pass ULTIMATE FAQ page you will get 50 days of Game Pass ULTIMATE added to your subscription with a 3 month Gold prepaid card.