[Serusers] Dial Plans

Hi, I need help with setting up a dial plan. Basically, I want to do this: If my phone #'s are 111-222-xxxx where xxxx is the extension, I want to be able to call xxxx instead of the full 10 digits when calling within the local loop. I tried looked for dial plans with SER online but found very little information. Any help is greatly appreciated. I've tried using prefix option without luck. This is what I had: if(!uri=~"sip:111.*") { prefix("111222"); }; When I try to call using just the extension, I get a busy tone. Are there any special modules I need? And are there any good tutorials on creating dial plans and how to set them up? I hope I posted the question to the right place, if not please let me know where I should ask. Thank you very much, Ben