Hi Naveed,
I would follow this approach...
i. Make sure all your contacts have a telephone number populated
ii. Then us WSP to add\show (readonly) the contact's telephone number.
<PDM_MACRO name=dtlReadonly hdr="Phone Number" attr=customer.phone_number>
This way there is no manual capturing of this on the actual ticket, instead you simply display the info as captured on the contact's detail ;-)
Kind Regards,
Brian