Please make sure to disable your Voxalot voicemail, if you are going to use your own answering machine.
http://www.voxalot.com/action/voicemail
Set Voicemail Active to No.
If the answering machine picks up but the caller still hears ringing, it sounds like a basic call not being established, and not an answering machine issue.
If you pick up the call before the answering machine picks up, does the call get established correctly and does the caller hear you?
Or does the caller still hear the phone ringing?