If you get a Fido account, it will say Fido.
If you get a Rogers account, it will say... 🙂
Which "number" do you want to put there? Your new phone number, so you don't forget it, and can give it to people quickly? I don't think you can do that.
How about a small piece of tape on the back, write your number on the tape, then another piece over that to seal it?
Maybe create a new contact?
If your new number is 604-555-1234, put the name as:
A 604 555 1234
with nothing in the number field.
"A" plus a space puts it first in the list, so you just push your "down arrow", and your number is right there.