Seths Blog says that "May I help you" is a completely useless thing to say - unless you want to end the conversation.
Seth Grodin is all about marketing and his point is that there are better ways for a marketer to begin a conversation. Certainly I don't feel particularly engaged when someone asks me this question.
And when your goal is to build a relationship, you don't want to end it at the beginning.
You also don't want to end it on a note of aggravation.
I find it both useless and irritating when an organization has been unable to resolve the issue I called about and my phone contact asks: "Is there anything else we can help you with?"
I would like to see the conversation end with, "We're so sorry we were unable to help you today."
A good next sentence would go something along the lines of: "I'll bring this to (my supervisor's/the owner's/the president's) attention and see if we can't prevent this happening again."
I believe you build more confidence and trust with clients and customers when you acknowledge the facts and indicate that the issue will be discussed after the call ends.
A couple of years ago, I was the customer whose complaint got lost in the telephone tree by my local internet company. My service had gone out and even though I called every day for two weeks, and different people made service appointments, no one ever showed up. Follow up calls showed no one had heard about my service being out and the process repeated itself.
No one ever apologized - not once. They did end each call with "Is there anything else I can do for you today?
After two weeks, a service supervisor called. He had learned of the unresolved service problems (It had something to do with the fact I had finally called to cancel my account) admitted they had dropped the ball, apologized profusely and gave me his direct work line so that if it ever happened again, I would never have to go through the phone tree.
It helped a lot to hear someone admit their error; he fixed the problem and gave me a means to prevent it happening again. I also got about a month of free service as part of the apology package.