first of all, the general mission of TR is for IT professionals to help other IT professionals.
Somehow, and I could be wrong, but helping you to hack into a broadband wireless carrier or someones private WLAN may not be exactly consistent with that mission.
You are confused as to what your friend is doing.
If he is stealing service from 'a tower', that would be a broadband wireless carrier, such as AT&T or Verizon. Not sure where you are, but there are two issues with this:
First of all, it's quite illegal. Not just local laws, we're talking serious Federal offense, ten years in Federal Prison. 18 U.S.C. 1362 and a whole bunch of other laws, including homeland security, etc.
In fact, tell us more about your 'friend' as the Feds can provide juicy rewards for turning in folks like this.
And if you think the RIAA or MPAA is heavy handed going after pirated music or movies, then you've not seen how a carrier will go after a service thief. The carriers also have assistance from the FCC, which tends to know a thing or two about radio.
Second, it's not technically possible.
While there are some known security issues with GSM networks, there are no known exploits that any script kiddie could use, period. There are 'things demonstrated by security researchers' that are valid, but these are light-years away from real-world exploits.
Even discussing wiretapping tools can be illegal in the U.S, software programs used for this purpose are as illegal, as is the hardware required to perform such hacking in the hands of a private individual. The bottom line is that a five or ten year timeout in a Federal Prison is more inconvenient than ponying up $20 a month for a wireless data plan.
With respect to WLAN hacking, there are no products you buy to do this.
You just need the open source programs to do that. However, keep in mind that this activity is also quite illegal in most jurisdictions, and one's ability to successfully hack into a private network will vary greatly depending on if encryption is disabled (very easy) to a more secure system like a Cisco 1200 AP using WPA2 with Cisco IDS and/or NAC. (difficult)