step  To recode 0's as missing values, from the menus choose:

Transform
  Recode
   Into Same Variables...

step  Select Long distance last month, Toll free last month, Equipment last month, Calling card last month, and Wireless last month as numeric variables.

step  Click Old and New Values.

step  Type 0 as the Old Value.

step  Select System-missing New Value.

step  Click Add.

step  Click Continue.

step  Click OK in the Recode into Same Variables dialog box.

Further analysis of each variable should now be considered conditional upon the customer's having the service.