Changing cellphone number

[mtbc]

It is safe to say that I already know my new cellphone number quite well having had to type it into so many websites, often multiple times. An interesting question is, which I forgot? I have covered banks, credit cards, brokerage, insurance, utilities, employer, online vendors, etc. Each of those can involve a few: e.g., for employer, I have the organization itself, the payroll processor, health insurance, dental insurance, providers for prescriptions, HSA, 401(k), etc. A fair few websites include SMS as multi-factor authentication in login so preferable would be changing the number before losing service on the old.