If the phone number is a mandatory field when the user signs up using the iframe Application then it will restrict you to remove the phone number from a guest profile in the platform and show an error.
For the Guests signed up using Mobile web, even if the phone number is mandatory field for sign up, removing a number from their profile is possible without facing any error.
If further assistance is required, submit a ticket to Punchh Support. (For help submitting a ticket, click here)