We always learn to give our customer the benefit of the doubt. It gains us nothing to be cynical or to assume everyone is exaggerating, if not lying, about problems. Try to see things from their point of view -- it can be upsetting to purchase goods or services that don't meet expectations, for whatever reason.
Even though it may appear that customers are trying to manipulate certain situations to their advantage, it's to our advantage to hear them out and try to help. The majority of customers don't like to complain; in fact, they'll go out of their way, perhaps all the way to a competitor, to avoid confrontation.
If we hear unhappy rumblings from our customers, take their complaints to heart and do our best to appease them.