Can I change the phone number on my account?

Yes, by email. Your number is how I know it is you, so if it changed I cannot tell over text that it is really you asking. Email [email protected] from the email address on your account and tell me the new number. I send one code back to that email and a second code by text to the new number, and when you reply with both I move your account across. If you no longer have that email address either, there is nothing left to check you against, and I would rather say so than pretend otherwise.