Leave word calling was a feature invented by AT&t before there was voice mail available universally. It was a method where a caller could call someone, and if they didn't answer, they could indicate that they had called. If you are using mode code intergration with your voice mail, then it uses LWC to turn on the lights, but otherwise remove the codes in the PBX so people don't accidently use them and cause U headaches.
Da-vi'do Juan-is'imo
P.S. For the best response to a question, read FAQ222-2244. Also give the type & version of your voice mail & pbx & preview your post to make sure it is complete & understandable. Please answer all questions so that I may have the info to assist you. Leaving a post on how you fixed the problem will also be appreciated.