How to Ring Before VM on Virtual Ext

How can we send a caller directly to VM while ensuring the hear a ringing sound for approximately 20 seconds? Some callers are a waste of time. Unfortunately, several types of callers tend to call back when they hear themselves sent directly to a VM box. We have a virtual extension for certain callers, and would like to direct them to that extension first, but, to help ensure they do not call back, we need to give them the impression that their call was attempted and did not answer.

create an IVR that plays ringing sound instead of announcement for as long as you want, then chuck them in the voicemail.

Also instead of virtual extension you can just use a "misc application"
You will need to have a recording of ring tone of a correct length in your recordings

create “misc application”, give it a name and a feature code
in destinations, pick “Announcement”->"Add New Announcement"
create an announcement with ringing-tone file, set “Repeat” to “Disable”. put the the desired voicemail destination at the end.

If you do this via manual transfer, then just have the call transferred to that new feature code. If it is done as an “inbound route”, you will need to set as destination “custom destination”->“add custom destination” and specify the feature code in there.