Analog phone not sending calls to voicemail on busy set

[Nogiealcatel]

Hi y'all.... I have a problem of analog sets not sending calls to the voice mail account when the user is on the phone and call-waiting is activated. Scenario is

1. No call waiting -- Calls go directly to voice mail if set is busy
2. Call waiting activated -- Calls camp on the set if busy but does not go to voice mail if nnot answered.

Does anyone have a solution for this?.. Please help. Thanks