The best way to protect your business from hungry competitors is to think of your business as a castle, and happy customers as a defensive moat around the perimeter that keeps the competition at bay.

If your customers are happy, your competitors must work twice as hard to entice them away. They're unlikely to switch for the sake of a few dollars, and they'll ignore unsolicited advertising shouting for their attention. 

Keeping customers happy starts and ends with looking at your business through the eyes of the customer. Put the customer first and give your team permission to care. The rest takes care of itself.