This phone does not have a sim card

I might not know what question to ask. can someone direct me in the right direction. Wanting to get all the benifits this phone has to offer and save$$$

Hello I have a samsung finesse and I heard that carriers lock the phones so you have to use there ringtones ect... was wanting to find info on getting other ringtones that my carrier doesnt offer can the phone be unlocked? Also I didn't see a sims card in the batterie compartment do they use the internal memory of the phone?
Thanks In Advance for any help