Game Pass Ultimate for £1 stacking on my Gold membership. Email saying I only get the 1st...

My brother and I were told that if we get Game Pass Ultimate for £1 we would have it until our Xbox Live Gold memberships expire and that one month would be added to our memberships, but my brother has recently received an email saying that he will be charged
£10.99 after the first month. The email goes as follows:

Thanks for subscribing to Xbox Game Pass Ultimate. We’re happy you’re here.

We've charged £1.00 to MasterCard [card] for your first first month of Xbox Game Pass Ultimate. For a full breakdown of charges, see your order details.

You'll be billed every month at £10.99 until you cancel. We'll email you ahead of time if that price ever changes.

Manage your subscription to review the latest info, change how you pay, request a refund or turn-off recurring billing to stop future charges through the manage subscription link below. You can also contact support.

Enjoy!

Please respond quickly as I need to know what, to do next ASAP.

:)