I have forgotten my password to change my username

See If you forgot your Apple ID password https://support.apple.com/en-us/HT201487

You also can use Having trouble signing in/iForgot

 https://iforgot.apple.com/password/verify/appleid

Go here if you need additional support Apple telephone support https://getsupport.apple.com/?caller=kbase&PGF=PGF63005&category_id=SC0245&symptom_id=23362

For worldwide Apple ID support go here https://support.apple.com/en-us/HT204169

Did you forget your user password?

User Password Reset.   

User Password Reset (2).         

User Password Reset – Apple ID.    

Did you try the reset suggestions I posted? Click on the links.

You are welcome.