Samsung SGH-C417 / C416
3G SIM CARD ISSUE
The new 3G chips ( the white/blue ones) have been having problems in the 417. Use the the White/orange stripe chips instead.
You might get folks complaining of the phone saying...CHECK SIM/INVALID SIM quite often
dropping calls, or missing calls as a result
It is not the phone, but the chip itself
I know our store had done like a dozen exchangews before we figured it out
Unfortunately Cingular no longer carries the sim cards needed for any C-417 having 3G network issues. The only thing you can really do is replace your phone under your warranty until you get one that works. also, it's not worth getting a different make and model, the only phns they can offer either don't have a camera, don't have bluetooth, or both.