Can i buy an unlocked iphone 4 from verizon and do this?

So i'm going to buy an verizon iphone 4 and i'm going to unlock it (its from verizon or sprint) i'm a little confused because i can't to put it on tmobile but they say it needs to be gsm. And they say if its unlocked it can be put on any companyb something like that so. Can i buy an verizon iphone 4 and unlock it and put it on t-mobile?

No, you can't. First of all, Verizon and Sprint use CDMA networks and devices, which are not compatible with GSM networks (T-Mobile, AT&T). Also, CDMA devices are not "locked", because thay have no SIM cards, so there's nothing to unlock.

So, no, you can't do this. By the way, even if the iPhone is a 4S, you can't do this.