It may be just the formatting of the phone number that TurboTax doesn't like. Delete what is on the screen and reenter just the 10 digits and let TurboTax format the number. If you type in 5555555555, TurboTax should format the number to be (555) 555-5555. And if you are entering a phone number on the payment screen, it may need to match that number from the My Info screen.