difference of 3650 unlock by store and unlock by code

some stores charge $25 to do the unclock, but I followed the Nokiafree.org guide and unlocked my friend's successfully, is it the samething? I figured it's really easy, but why they charge that much?
some one said it's not the same between unlock by store and unlock bu inputting the code.
so, why? what's the different?
simply, if I unlock the cellphone by dialing the unlock code, can I use it when I travel to China and go with a Chinese telecom Company? or I have to unlock by using hardware device? such as have it unlock in stores?
thanks! please reply soon

The unlocking at a store is the same as the unlocking here on nokiafree.org.
the only thing difference is that here its free.

And it can be used with any sim card nomatter where it is from

:P
thank you very much!

you are welcome

pass on the Word
OK