my answering machine says to all incoming calls that the mailbox is full even though it is empty. Therefore incoming calls are not recorded.

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In standby mode (not on a call), press the DELETE button on the main base station. This is the icon that looks like a 0 with a slash through it( Ø ) just to the left of the answer on/off button. After pressing that delete button press the soft key for Line 1. Repeat the process with Delete again, then press the soft key for Line 2. This will clear all messages on the built in answering machine.

Also may I have the model number of your phone?

I am trying to call you back.  Please le tm eknow when your phone line is plugged back in.

I am getting the same message that the mailbox is full.  Please call me back at ***-***-****

I called custoker and customer says voicemail is now working so far.  Customer asked to wait until Tuesday to give phone time to see if the device will continue working.  Customer asked for a call back Tuesday.

Dear Scott, It was a pleasure attempting to help you with your Uniden issue today. I regret we were unable to offer you the most helpful answer. I have escalated your question for a second opinion. We appreciate your patience. You will be notified via email when a new Expert contacts you for continued support for your issue

I tried to call customer, but unable to leave voicemail.

Dear Scott, It was a pleasure helping you with your Uniden issue today. Here is a summary of the resolution. 
Issue identified: Customer voicemail is not working.
Solution Implemented: I called customer and sent replies on how to resolve issue.  I followed up with customer today and answering machine is still working as of now.  Problem solved.
If issue resurfaces: Please follow the same steps again if the issue resurfaces. Also you can contact support by email at s**t@experthelp.com or by phone at ***-***-****