I think starting with a good reservation software system is important. One that is modern and congruent with peoples desire to respond, or in this case lack of desire to cancel their reservation. Easy options for texting back and forth to confirm and remind the customer of their reservation. A diligent host or hostess is important as well, he or she can call the customer when they get to work after the automated reservation system has sent messages to each reservation at specific and appropriate times throughout the day of their reservation. People don’t want to talk to anyone these days. It’s sad but true. But a simple text message (one that they can respond to) is a good choice.