Short-Term vs Long-Term Selling Strategy

Maybe I’m just on a streak, but it seems like I have been experiencing more and more salespeople/service providers who overpromise and under deliver, coming back after the fact with arguments about schedule and cost. 
 
I am getting the feeling that this is part of some companies’ strategies but “SELLER BEWARE!”
 
The old bait and switch is probably the worst, long-term relationship building strategy I can think of, particularly now that people can post their reviews on Yelp and other online review sites. I also notice that companies that overpromise and under deliver usually disappear over time. 
 
I would definitely prefer to see salespeople and service providers under promise and over deliver, even surprising and delighting clients well after the transaction. 
 
Long-term relationships live and die with trust. Break trust and you will have to replace a client . . . which is always more expensive than taking care of your existing ones.