Updating email address

I'm trying to update my email address. Xfinity app wants to send a code to verify. Im on android, I don't have a computer, my phone is all I've got. When I minimize the Xfinity app to go to Gmail to retrieve the code and go back to the app to enter code, it refreshes and sends a different code so the one I've got, is now worth nothing, no good, notta....it's a never ending run around....I've tried so many times it kicked me out, it says number of chances were exceeded and tossed me to the curb....