Cell phones are notorious for poor sound quality. They also cut in and out. So when you use your cell phone to leave a message for someone, speak slowly and deliberately, say your callback number slowly and deliberately, and you may even have to spell your name, especially if it is one that will be unfamiliar to the person you are calling. Also, you must repeat your name and number because if the sound cuts out, the person on the other end may actually miss the most important part of what was said (your name and number. Finally, if you don't hear back from the person, you may want to try again because it's quite possible they just couldn't hear or understand your voice message.