One time when I was working in a call centre dealing with one irritating customer who would never be satisfied with my service (unless I literally broke the law to give him what he was asking for), the following exchange took place.
Me: I'm sorry, there's nothing more I can do to assist you with your request. I have checked with my manager who agrees what you're asking cannot be done. He can't speak with you directly right now, but if you'd like, he can call you back later to confirm.
Customer: That isn't good enough! You're not providing me with very good customer service!
Me: That is a reflection of what I'm forced to deal with. You're not a very good customer.
Yes, I stole the line from acts of Gord. No, I didn't get fired.
Me: I'm sorry, there's nothing more I can do to assist you with your request. I have checked with my manager who agrees what you're asking cannot be done. He can't speak with you directly right now, but if you'd like, he can call you back later to confirm.
Customer: That isn't good enough! You're not providing me with very good customer service!
Me: That is a reflection of what I'm forced to deal with. You're not a very good customer.
Yes, I stole the line from acts of Gord. No, I didn't get fired.