Real-Time AI Voice Assistant for Phone Calls (Commercial Use)

Hello, I am looking to build a production-ready AI voice assistant that can handle real-time phone calls. The system will be used for business clients and resold commercially. Core requirements: - Real-time voice conversations - Automatic call answering (inbound) - Speech recognition and natural voice responses - Stable, scalable backend - Easy deployment and maintenance - Full commercial usage and reselling rights Important conditions: - I must have the right to resell the solution to my own clients - The system must be delivered as a custom solution (not locked to a proprietary platform without access) - No mandatory monthly fee after delivery unless explicitly agreed - Clear documentation or handover after completion Please include in your response: - Your experience with similar AI voice or calling systems - A short explanation of the technical approach you would recommend - Estimated timeline - Estimated total cost This is a serious long-term project and can lead to extended collaboration if the first version goes well.