You give the carrier the ESN of the phone you want to use and they will either give you the programming instructions or tell you that the phone cannot be activated on their network. Here is a list of Cricket phones with programming instructions: Cricket Phone Programming Instructions There is a link on the page for other phones acceptable to Cricket.
CDMA and TDMA phones are not locked, per se. These networks will only accept certain model phones based upon the ESN. Since the carrier has to link the phone's ESN to the phone nuraber, you cannot activate a phone for use on those networks without the cooperation of the wireless carrier. You could program the phone nuraber and carrier System Identification Nuraber (SID) into the phone but it will not ring unless the carrier assigns your phone nuraber to it on its network.
At $300! Its been around with Alltel for a while and I think the price went down!
With that being said, does anyone know where I can buy the phone "cricKet Ready" third party? I know you can get them cheaper than from the company. Could I buy one from Motorola cheaper?