To ensure that the Passengers get the link to get updates on their ride request or schedule a ride back to the dealership, the Service Advisor needs to put in the correct phone number. However, if the Passenger has the right phone number, but they are still not getting any message after the ride has got scheduled, it's because:
They have opted-out from receiving messages from your dealership in the past. If the customer decides to opt-out from receiving messages, they can do so by replying "Stop." But, if they select "Stop," it means that they will no longer receive any messages in the future.
They have turned on a setting in their phone to block particular messages from being received.
Their network provider blocked the messages.