So today my a friend of mine gave me his blackberry 8700g I put my Sim Card which was previously in a Motorolla phone but when i connect to the wireless the Connection successfully connects to "GSM EDGE" but after a few seconds the words dissapear and when i try and make a call it won't let me and won't let me do anything but the blue bar is still full.

What am i doing wrong?

Is the 8700g unlocked?

I also inherited an 8700 and used a prior SIM card from AT&T. I had to "Clean" the phone and then install the most recent OS. It was 4.2 but has since been upgraded again. My phone works fine. Hope this helps.