AI Buddy uses GPT-3 to hold a pretty decent conversation (Users have to bring their own OpenAI keys). It holds a memory of last 5 conversations currently.
Few planned improvements in near future.

Running this for WhatsApp is a bit expensive for both the maker and the users), So the next plan is built this for telegram.
Let users choose different personas for the AI.
Let users choose how much conversation memory they want the bot to hold for them(more memory means more tokens means bigger bill from OpenAI)
Let users bring in their own data to fine-tune GPT-3 for a custom bot. For example, a bot trained on a writer’s work or even your own.

A product by FortyTwoAI
The maker can hook people up with some codes to try it out: just drop an email at aibuddy.chat@gmail.com