Phone number isn't the same so I can't buy Xbox live, how do I change it

Hello, first it's a pleasure to be able to help you today.

My name is welcome to the community.

Hello Sam, by its description it should be referring to the phone number that you entered as security information, to change it you must do it through the link below by logging into your account.

Security

https://account.microsoft.com/security

Note: do not delete a security number or email, you must first add a new phone number or email and then remove the old one.

I have the same issue, so annoying. I only wanted to change my phone number. And now i can't log in on my xbox.

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1. Sign in to your account using your existing alias and password.
2. Go to Your info at the top of the page.
3. Select Manage how you sign in to Microsoft.
4. You may be asked to verify your account before changes can be made. Follow the instructions provided to select your alias:
   • Select Add email. You can create either a new Outlook.com email address or add an address that you already have. Then, select Add alias. You’ll be returned to the previous screen. Select Verify and
     follow the instructions provided.
   • Or, select Add phone number. Enter the phone number you want to use, and then select Next. When you add a new phone number, we'll send a text message to that number to verify it. Enter the code in the text message, and
     then select Next.
     Note Email addresses and phone numbers that are already an alias on another account can’t be used.
     

It can take up to 48 hours for the change to be implemented across all Microsoft services. If you sign in to your Microsoft account on an Xbox One console by using your Kinect sensor, you might temporarily
be asked to manually sign in with a controller. If you're still being asked to manually sign in after 2 days, try removing your account from the console and then adding it back.
You can use any email address or phone number you have listed as an alias to sign in. To make it harder for someone to break into your account, change your sign-in preferences to turn off any alias
you don't want used to sign in.

I have a similar situation

I am locked out of my account basically..

I'd go to sign in, put my password in then it comes up with security info thing where it texts a code to my number

But that number isn't mine, it is my boyfriends. (I used his number coz I had very bad phone service) and he has lost his phone so now I can't get the code to sign in....

Do you know how to change that number (if you even can) ?