As with any business, especially in retailing, your service methods are an integral part of your business plan that can make or break the relationship between you and your customers. Therefore, it's up to you to do everything in your power to ensure that they are getting what they want, and when they want it (within reason). Perhaps this article from Inc. can serve you some guidance.
Without customers, you'd probably go out of business very quickly. By treating your customers the right way, you can avoid such an inevitable fact. Remember- first impressions are crucial in any business environment.
You can read more here in the article from Inc.