I am not sure that prepaid plans are necessarily less expensive.
The problem with contract plans is that people over-estimate how many minutes they need.
I don't talk much on the phone so the least expensive calling plan is fine for me.
I use a free texting APP on my iphone so I don't pay for any texts.
I would have gone with the least expensive data plan because I use data mostly through WiFi and check emails on the 3G network but my discount doesn't apply to the leasat expensive data plan so I opted for the higher one which cost the same.
When I looked at prepaid plans, my monthly bill was lower with a contract plan.
I do have a corporate discount but my friend who works someplace else asked if there was any corporate discount for her company and it turned out there was. If you work for any kind of corporation, it doesn't hurt to ask. My discount is 30% but her discount is 20%.