I believe that the cost depends on your cell provider. I think most these days include it (I know my Verizon does) but check with them first to see if you have free call forwarding.

Here are some deactivation codes:

DIRECTIONS:

   1. Find your deactivation code in the table below.

   2. Enter the first code exactly as written, as if you're dialing someone.

   3. Press "Send" on your phone to dial that number.

   4. If multiple codes are given, repeat steps 2 & 3 for each code


Wireless Carrier or Network ---> Deactivation Code
AT&T Cingular, T-Mobile, GSM network: ##004#
Verizon (CDMA network): *73 AND *900 AND *920
Verizon (TDMA Network): *740 AND *730
Bluegrass Cellular: *900 AND *920
Cellcom: *680
Cincinnati Bell: ##004#
US Cellular: *740