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

Transform
Recode
Into Same Variables...

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

Click Old and New Values.

Type 0 as the Old Value.

Select System-missing New Value.

Click Add.

Click Continue.

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.