To update your phone number or email address, tap the Click-to-Call or Click-to-Email widget button and select Edit from the pop-up menu.

You can then choose the phone number or e-mail and the text on the button:  

Note: Click-to-Call links are only active on devices that support direct calling.

If more than one phone number or email address is available, select the one you want to update from the drop-down menu and continue editing as described above.