Dumping the small clients when better ones knock on the door

We paid and booked with Window Art for vinal on a bathroom window. The builders were late, and we rescheduled way in advance. On all of the written correspondence the T&C's they indicated a 14-day lead time which was also verbally confirmed. When we tried to book again after a couple of day's we were told they got in some good new deals and that the T&C's has been amended to please them. The result was that we had to find another company to do it, since we wouldn't be able to move into the house without it. It is a small job and they still need to learn the value of respect towards all customers and not give the minor ones the attitude they did when a bigger, better deal comes along. They did however refund us within a reasonable time.