How many of you have an iphone?  How many of you use t-mobile as your cellphone provider?
So i went with a friend to a tmobile store so he could cancel his phone account, because my friend was switching to AT&T to get an Iphone. The guy at T-mobile told us that he would jailbreak the Iphone and use T-mobile network instead of AT&T.  I was told it would save me $60 a month!
 
Now... Have any of you done this?? is it worth it is it reliable??

He wouldn't jailbreak it, he would simply unlock it so that it could be used wiht any provider that uses SIM cards.
 
If he were to jailbreak it, then you should report him. Jail breaking is fine, but for an employee to endorse it is bad business.
 
Check AT&T plans before doing anything though.

AT&T iphone plans are hella expensive, but there are a few apps out there that allow you to call over wi-fi. If you're constantly near wi-fi hotspots or have constant access to wi-fi, then you can cut down costs dramatically by getting the least minutes possible (at least i think you can, I haven't really looked at iphone plans). And since it's in the app store, it's been approved by apple and might help you save more money, legally.