CalliFy is the 1st tweak that allows you to change the text of your call button without having to SSH. It’s simple to use but you can’t use more then 4 characters or special characters since the call button isn’t that big. This only works for iPhone since it’s the only iDevice where you can use the Phone app. For support on this tweak plaese use the link below that says support twitter to get support.
Configure options from Settings app