It really depends on the caller. A majority of the time, people recognize that they are speaking with AI. Other times, some people don't realize that it is AI.
Either way, people do have full conversations with it over the phone.
The AI voices in our library are also designed to sound as natural and human as possible. You can check out our voices library on this page here: https://upfirst.ai/voices.
We also conducted a study that showed that disclosing in your greeting that it is an AI or virtual assistant resulted in fewer hang ups. So, the best practice is to be up front with your callers that they are speaking with an AI assistant.