Flashing an Iphone 4S

A friend recently gave me her Iphone 4S(on verizon) and i have cricket. I know its possible to flash from verizon or sprint to cricket.
Here's the problem, i found a flashing store near me and their site says they can flash an iphone 4s, well when i emailed them to confirm how much it would cost they tell me they can't flash the iphone 4s ONLY the iphone 4?
Can someone please explain why?
Thanks!

Added (1). I've received mixed answers about this. People has said that they have flashed the iphone 4s and there are videos on youtube showing it being doe but this "flash" guy said its not possible with iphone 4s…
I'm really confused. The only thing different about iphone 4 from the 4s is: better signal strength, siri, battery, and the camera.

That doesn't really make much sense but maybe it's because the 4S is the newer one and the just can't do that yet.

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