Hi @Raphael_Blot and @samliew thank you for the guidance. I redo my scenario followed what has been shared by @Raphael_Blot above and managed to come out with a successful chat completion in Whatsapp.
For the issue on only getting “Accepted” response, I have took guidance from the post here: Webhook replays "Accepted" (Reopen Topic) - #11 by Rafael_Sanchez
Thanks again Guru’s! Appreciate it 