I need an expert in PLC, API and App Development

I’m looking for someone to help me with a project which involves PLC, API and App development. I have 6 sauna machines, they have a keypad to turn them on/off and button to adjust temperature. I need a PLC to control this remotely which will interface with a booking system. When a customer books a session this will preheat the sauna 10 to 20 minute prior and turn off the sauna after booking end time. They book through a custom mobile app which they need to create an account first. I also need to integrate a card access system which I have an API for. I have attached a flow diagram to completely explain the work.