Can you use a mask on phone to prevent text on existing contacts?

Topic by Paul Howard

I have applied a mask (M#M#M#M#M#M#M#M#M#M#M#) to the Internationalization --> Countries --> Phone Mask.  This prevents the agents from putting text or any symbols into a new contact's phone number.

However, if I open an existing contact and attempt to amend the phone number, it will let me change to letters, symbols and longer than I have stated at 11 numbers long.

Have I missed something here?

Thanks!

Paul