As of the latest update, there is no specific company named "Retell AI" found in common business databases or through a web search on its provided URL, https://www.retellai.com. The site might be newly established, under development, or not indexed effectively in major search engines. Therefore, no accurate description or details about the business activities, offerings, or background of "Retell AI" can be provided without additional information. If "Retell AI" is a startup or a company in stealth mode, it would be beneficial to check directly at the provided URL for the most current details or for any official announcements from the company.