How Do I Get My Voice Mail To Work On My Lg 800g?

I've been trying to get my voicemail to work on my new phone. When I enter the password it tells me that it is incorrect. Yesterday I called customer service and was told that my password would be reset to the default setting which is the last 4 digits of my phone number. I was told to wait at least 4 hours before trying it again. I waited 16 hours and tried it this morning but was told that the password was incorrect. What should I do now?