How to change my cell phone number to receive 2FA codes???

Due to a fraud attack, I now have a new cell phone and a new phone number. I have not figured out how to change the phone number in my Microsoft account for receiving 2FA authentication codes. On March 13, I spent several hours try to do that with the aid of Copilot M365, and did not succeed. Access to change the phone number is deeply buried under levels of security. Apparently running the system passwordless is a major complication. I am using a brand new SP12 (also acquired due to the same fraud attack), Windows 11 Home build 28000.2340 . Any advice would be welcome.