Someone activated a prepaid Xbox LIVE Gold subscription using my email address

Not sure what to make of this. Have you tried logging in to commerce.microsoft.com with your gmail account to see if you can get in?

Either way, you may need to contact phone support for more help with this billing issue. If you live in North America then dial 1-800-469-9269

Currently I have Game Pass Ultimate subscription with recurring billing off and don't want this subscription service once it expires 10/22/22, so do I just activate my prepaid xbox live gold subscription card on 10/23/22, or do I actually have to cancel game pass ultimate subscription for my account on 10/23/22 manually before redeeming and activating my xbox live gold prepaid 12 month card on 10/23/22?

Also, if you select turn off recurring billing on your account for your current game pass ultimate subscription, does that automatically cancel your prepaid game pass ultimate subscription on its expiration date? or is it requirement that you still manually cancel Game Pass Ultimate on or after its prepaid expiration date if you wish to switch back to xbox live gold using a prepaid subscription card?

When i used the link it took me to a web page with said old email address saying that they had emailed me a code to it. once I had used it and logged in I saw that on the subscription page, showed my current gold membership with old email address next to
it along with my MW3 prepaid membership.

Currently I have Game Pass Ultimate subscription with recurring billing off and don't want this subscription service once it expires 10/22/22, so do I just activate my prepaid xbox live gold subscription card on 10/23/22, or do I actually have to cancel game pass ultimate subscription for my account on 10/23/22 manually before redeeming and activating my xbox live gold prepaid 12 month card on 10/23/22?

Also, if you select turn off recurring billing on your account for your current game pass ultimate subscription, does that automatically cancel your prepaid game pass ultimate subscription on its expiration date? or is it requirement that you still manually cancel Game Pass Ultimate on or after its prepaid expiration date if you wish to switch back to xbox live gold using a prepaid subscription card?

If, at a later date, I want to consider switching back to game pass ultimate service again after already activating up to 36 months of prepaid xbox live gold subscription cards, then the option to convert these 36 months of xbox live gold to game pass ultimate at a 1:1 monthly ratio conversion for a 2nd time all over again is still offered to me correct? the only difference this time around would be that I would have to pay $14.99 or whatever the current monthly game pass ultimate price rate is for one month to convert all prepaid live gold months at 1:1 ratio? since I can't qualify for the $1 per month ultimate promo price deal since I already used that 3 years prior?

Some games or console bundles may include a prepaid code for a 2, 3, or 14 day Xbox Live Gold trial subscription. This trial subscription starts as soon as you activate the prepaid card.

The following limitations and restrictions apply to Xbox Live trial subscriptions from games or console bundles:

• If you have an existing paid Xbox Live Gold subscription, you can’t redeem Xbox Live Gold trial subscriptions from games or console bundles to extend your subscription period. However, you can redeem the prepaid code once your current paid subscription
  expires.
• Prepaid codes for Xbox Live Gold trial subscriptions are only available in select games and bundles.
• You can’t access Games with Gold for the Xbox 360 with this type of Xbox Live Gold trial subscription.
  
• You can’t stack prepaid codes for Xbox Live Gold trial subscriptions from games or console bundles. This means that you can’t start another trial period before your current trial period has finished. However, you can purchase a new paid Xbox Live Gold subscription
  and start the subscription at any time during the trial period.
• If you don’t currently have a paid Xbox Live Gold subscription, there is no limit to the number of times you can use this type of Xbox Live Gold trial subscription.