Automation Case Study
Inbound receptionist and outbound calling agents with scheduling tools, conversation controls and Twilio SIP telephony for medical spa operations.
Medical Spa · Client identifiers removed
Case Study At A Glance
Business Objective
The medical spa needed an AI voice system that could answer service questions, check availability, book appointments, and handle outbound follow-up calls — all while maintaining a warm, professional receptionist experience.
Separate inbound and outbound agents were configured to handle different conversation scenarios with consistent scheduling logic.
Implementation Scope
The implementation combines Retell AI inbound and outbound agents, Twilio SIP telephony, appointment booking functions, conversation tuning, and service-aware scheduling logic.
Call Flow
The system uses separate Retell AI agents for inbound and outbound calls, connected through Twilio SIP telephony.
Customer calls the medical spa phone number. The call is routed through Twilio SIP trunk to Retell AI.
TriggerRetell AI inbound agent answers with a warm, professional receptionist tone. Answers brief service questions and guides toward booking.
ConversationThe agent uses the check_cal_availability function to find open slots. Requires user-confirmed date and time before proceeding.
Function CallAfter user confirmation, book_appointment is triggered with RFC3339 datetime. Confirmation is sent to the customer.
ActionSeparate outbound agent handles confirmation calls, reminders, and callback handling using dynamic caller fields.
OutboundAgent Comparison
Speech & Call Tuning
Response timing, interruption behavior, denoising, transcription mode and call controls are explicitly tuned inside Retell AI.
Responsiveness and interruption sensitivity are set explicitly rather than left as generic defaults.
The inbound agent is configured with a call-center background sound setting for optimal clarity.
Noise removal is enabled and the transcription mode is set to optimize for speed.
User keypad input detection is enabled with a configured timeout for seamless DTMF interaction.
Technology Responsibilities
Voice Agent
Inbound receptionist and outbound calling agents with booking functions, variable extraction, and conversation tuning controls.
Telephony
Elastic SIP trunk for PSTN routing, origination and termination connectivity, and US phone number assignment.
Verified Outcome
The implementation demonstrates Retell AI inbound and outbound agent configuration, prompt engineering, dynamic variables, service-aware booking logic, and Twilio SIP telephony.
Call volume, booking conversion, revenue and other performance metrics were not supplied. This case study focuses on the implementation evidence and verified agent configuration.
Technical FAQ
The inbound agent uses two callable functions: check_cal_availability to verify open slots and book_appointment to schedule. Both functions require a user-confirmed date and time before triggering, preventing premature bookings.
The inbound agent handles incoming calls for service questions and bookings. The outbound agent handles follow-up calls with dynamic caller fields for identity confirmation, timing checks, and callback paths when the timing isn't suitable.
Twilio is configured with an Elastic SIP trunk named for Retell integration. It handles origination (inbound SIP traffic toward Retell) and termination (outbound PSTN routing) with a US phone number assigned under the trunk.
Response behavior, interruption sensitivity, call-center background sound, noise removal, transcription mode (optimized for speed), keypad input detection with timeout, silence handling, and maximum call duration controls were all explicitly configured.
Current-time context is passed through a dynamic variable and interpreted in US Eastern Time. Internal date/time rules specify an absolute RFC3339 datetime with offset for function calls, ensuring consistent interpretation.
Related Automation Services
Talha Rehamni builds AI voice agents, Twilio telephony integrations, and conversational booking systems for medical spas, clinics, and service businesses.