The next time someone says you are very nice, don't start flattering yourself! There must be a reason why Dictionary.com describes the origin of the word as "1250–1300; Middle English: foolish, stupid < Old French: silly, simple< Latin nescius ignorant, incapable, equivalent to ne- negative prefix+ sci- (stem of scīre to know; see science) + -us adj. suffix."
In a service environment, the word "nice" is used to compliment someone when the customer is very happy with the service. So if you want to be called nice, just keep pampering your customer by providing extra care and service with no extra charge. Is that being nice.... or perhaps that is being overly generous with your company's time?
In truth, when a person says you are nice, it really means he likes your service, not you. To prove this point, imagine that you make a serious mistake involving the customer. Will he still think you are nice? Or if you simply carry out your duties without providing first class service, will he still think you are nice?
By all means, be nice to everyone at all times. Just don't let it go to your head if you receive a nice compliment. If a compliment comes from doing something for someone, that person is just complimenting you for the benefit he has obtained from you.
So when someone pays you a compliment, he may be paying you in compliment. And compliments are free. Are you nice or are you used?