I found a cingular raze with a sim card its unloced but the sim is bad can i buy

A sim card will only work when you have a service provider. It Links a certain phone # to that phone.

You can buy a sim card from any provider you like, but you'll need to buy one that is from the provider whose network you want to use. A T-Mobile sim card wouldn't work on AT&T's network, for instance, or vice-versa. I wouldn't buy a sim from eBay unless you are SURE it is new; a brand new one is just not that much money (usually $20 or so, tops from a carrier's store), and with a new one, you'll know it works on YOUR network.

Assuming you have the appropriate sim card, the phone should work just fine. Once in a while, an unlocked phone will not work, but that's usually off-brand phones (Chinese-made phones sometimes have REAL problems, for instance). Motorolas generally do just fine.