Agreeing to provide a service on a specific date, then offering the same service to others, and withdrawing from the first agreement upon receipt of a better of

Agreeing to provide a service on a specific date, then offering the same service to others, and withdrawing from the first agreement upon receipt of a better offer is wrong. You might not agree with that, but it's how I see things. What would you think if the companies and individuals you interacted with were constantly backing out of signed deals?