If you are in customer service, first, quit apologizing for the inconvenience. If you can’t do that because the boss is around, then here is the ENTIRE formula:
Hear them out (fully, let them run out of steam if needed)
Apologize for the inconvenience
Empathize. I know how frustrating this must be for you
Take action. I promise, we will resolve this during this phone call.
Not hard, but if you don’t do H, E or T, apologizing for the inconvenience just pisses the customer off even more.