Why is my 12-month Gold card trying to convert to 4 months of Game Pass when I try to...

and when i redeem a 12 month game pass card it converts to 4 months i basically get scammed

Are you sure it wasn't a Live Gold card? As I have seen before (I think) where 12 months of Live Gold gets turned into 4 months of Ultimate Games Pass.

Since Game Pass Ultimate includes Gold, when you add a Gold card to an Ultimate subscription, it converts the Gold to Ultimate as well. Since 12 months of Gold is equal in price to 4 months of Ultimate, that is what it converts it to. In order to use a full 12 month Gold card, you have to either cancel your Ultimate subscription or let it fully expire before adding the new card.

Yes the auto renewal is off already. I have the Game pass ultimate until May 25. I already bought a new 12 month xbox live gold card but when I try to redeem the code it says my 12 month
gold will be automatically convert to a 4 months xbox game pass ultimate which I don't want. I want the 12 month of xbox live without the game pass. Do I really have to wait until my xbox game pass expired before I can redeem a new xbox live gold (without
the game pass ultimate)?

If it converted to Ultimate, that means you already had Ultimate on your account when you added it. Since Ultimate includes Gold, it will convert any regular Gold or Game Pass cards to Ultimate when you add it to your existed subscription. It converts the subscription based on price rather than time. 12 months of Gold is equal to 4 months of Ultimate, which is why you only got 4 months instead of 12 (It does also warn you of this when you add the card). In order to get the full amount of a prepaid card, you would have needed to either cancel your Ultimate subscription or wait for it to run out before adding the Gold card.

Yes and no. The card will convert to Ultimate, but not for 12 months. A 12 month gold card will be converted to 4 months of Ultimate per the conversion rate in the FAQ.