My experience on address change.

1.go online, fill out all forms (employer information is option online) https://egov.uscis.gov/crisgwi/go?action=coa

1.(alternative): call CIS directly, ask 2nd level rep to change address for you.

2.go post office, fill out change address form, they will transfer all your mails from your old to your new.

3. after about 2 weeks, call CIS to check if address is updated in the system. (normally take 5 business days)