What version 2.2, 2.3, 2.3.1, etc.?
If 2.3 or higher, PID-13 is an XTN type field. With that there is a component which describes the type of Telecommunication equipment and CP is for Cell Phone.
For backward compatability the first occurence of the field is the primary telephone number (but could be Cell or other). Also the telephone number itself is to be formatted or componetized such as:
(718)428-3333^PRN^PH