No offense, but I probably wouldn't pay for that work either. I don't say that to be mean, just saying that maybe the quality of work was not up to the standards they were expecting. And so they chose not to pay for the final product.
Going forward, try to work out an agreement ahead of time. Specify the work being done, how many revisions are allowed, how much the customer is paying, who owns the intellectual property, etc. And try to get some type of down payment up front. This is sometimes a touchy issue, since the customer doesn't always know what they are getting until after the work is done. But you as the designer should be able to show samples of your previous work. If the customer is not satisfied, they can walk away at that point and no harm is done. If they are satisfied, they should at least be willing to make a 25-50% deposit.
Going forward, try to work out an agreement ahead of time. Specify the work being done, how many revisions are allowed, how much the customer is paying, who owns the intellectual property, etc. And try to get some type of down payment up front. This is sometimes a touchy issue, since the customer doesn't always know what they are getting until after the work is done. But you as the designer should be able to show samples of your previous work. If the customer is not satisfied, they can walk away at that point and no harm is done. If they are satisfied, they should at least be willing to make a 25-50% deposit.