Has anybody used AI calling agents for your business?

Has anybody used tools like synthflow to create a an assistant and call your clients?

I created one for my business, and I tweaked it a little bit to not sound like a robot and so far is doing great but not perfect. It answers all questions and objections on point, but I'm still looking to make it more human even though it won't ever be "perfect." Are there any prompts that you guys are using? Like telling it to use certain Voice intonations? Has any of your clients hung up or found out it was an AI? I'm about to test this for my real estate business and any insight or tips are appreciated!