Chat via SMS ran by Zapier with Open ai integration

Hi, ive started a chat via text that people subscribe to to receive weekly messages and i wanted to add a feature that they could text the number and an ai chatbot would give an answer solely pulling information from a book I wrote and nothing else. I played around with zapier and chat gpt for a while, but the answers were always terrible at best. Looking for someone who can put together a better product, so the answers can be spot on. I've been using Zapier's Copilot so far and the answers, as I said, are quite poor.