Changing phone number associated with your Microsoft account
Step 1: First of all, head over to this page of Microsoft in a web browser. As always, sign in to your Microsoft account.
Step 2: Once you sign-in, you will see the following page with various details about your Microsoft account. Click the Security tab.
Step 3: On this page, you should see options to change your password, update security information, and review recent activity. Click Update info button.
Step 4: Clicking the Update info button will take you to the following page where you need to verify your identity by either selecting your current contact number or secondary email address.
Choose one of the options, enter last four digits of your phone number currently associated with your Microsoft account or type the secondary email address, and then click Send code button to receive the verification code to your phone number or secondary email address.
Step 5: Type in the verification code. Click the Submit button to verify your identity.
Step 6: Upon successfully verifying your identity, you will see this page with security information. To change your Microsoft account phone number, click the Remove link next to your contact number. If you don’t have a contact number for your account, skip to the next step to add one.
When you see the confirmation dialog, click Remove button to remove the phone number from your account.
Step 7: Now, on the same page, click Add security info link.
Step 8: Select A phone number from the first drop-down box, select your country, enter your phone number which you want to associate with your Microsoft account, and select a method to verify the contact number (text or call).
Click Next button.
Step 9: If you have chosen text method to verify your number, you will receive a code to your phone. Finally, enter the code received on the phone in the field and then click Next button. And if you opted for a call, you will receive a call from Microsoft to verify the contact number. That’s it! You have successfully changed or added your phone number to your Microsoft account.
If you want to receive alerts (when Microsoft finds unusual activity on your account), click Change alert options link on the same page, and simply check the box next to your phone number.
Hope you find this guide helpful!