If you were to just do that, the calls would not reach you personally, they would all reach the 3CX system so it would not give the desired effect.
It can be done but the only way to do it would be to:
deploy a full 3CX phone system
set up the Telnyx trunk on it
set up your rules and call routing
setup an extension for yourself
setup your extension to go to 3CX voicemail when you are offline or unavailable or DND
use the 3CX app to access the extension for making/receiving calls + voicemail
It can definitely work this way, but it's a bit overkill to be honest for just a single user
You might have better luck setting up the Telnyx trunk on a device like say a personal router installed in your home that supports SIP lines and has built in voicemail storage.
I migrated to amazon and now i have two pbx the trial one with you and amazon. How do i get rid of the trial one? Could two pbx be causing me issues too?