Alright, I solve the requirenment by creating a Public group so that users can send 1:1 action cards to the admins, and then using the "Send message to group" Kaizala action from Flow to respond. In that Action you can specify the users phone number so you can emulate a 1:1 chat.
We currently has a Issue Reporting (Form Action) in a Private Group. Once a member submitted the Form Action, it would be send to admin. We use Flow, to automate 3 parallel actions which one of it, returning an Image Action, with arranged Caption (data from the submitted Form) to the same Private Group. I realized that, the returning Action will always have the Flow/Connector's Owner Name on-top rather than whoever submitted the Action Form in the first place.
Is your Subscriber field would solve my issue there?