Extra characters showing up on phone number field

When I enter the area code and phone number of the event coordinator and extra comma is showing up on my form that is sent via email is there any way to correct this and/or to validate that only a three digit area code has been entered and phone number appears to be valid

I can see you have switched the field to use an input mask, that's the only way to currently force the users to enter certain number of characters in the area field. 

I have checked your account email history and noticed the extra character does not show up, may you please confirm if using the input mask worked?