In the server validation for the phone number, you can set the phone number format to allow. 
is this on the confirm.asp page? if so, when i double click server validations and the one that is for the telephone, I only have 3 options to change and 2 of those are greyed out (allow intl (greyed out), force area code (greyed out) and allow blank entry)
you can add additional validations for the fields to the server validation behavior. 
what would I set as the trigger as this would be before they click on the checkout button..?
for each validation that you add, make sure to add a validation show if to the checkout page so that you know which form fields are failing validation.It sounds to me like you have some validations in place that do not have a corresponding validation show if to show what is failing validation.

all the validations have definitely got a valifdation show if
i am getting myself tied up in knots with this


