Hi there, I have finished setting up my AI voice receptionist in retell AI, I'm using the OpenAI gpt 4.1 fast as the LLM, what other setting do you adjust to make the voice sound clearer? When I test the agent it sounds very robotic, I have mentioned in my prompt specifically to make human like conversation. Not sure what else to do, any advice gents?

Has anyone else encountered this error when trying to run the ai booking receptionist? ( the one that schedules, reschedules and cancels bookings) Error: 400 Bad Request - {"message":"custom in 'startTime': startTime must be a valid date string; custom in 'endTime': endTime must be a valid date string; custom in 'endTime': endTime must be after startTime","data":null}