Think about this. A customer service person answered my call about a product I pay for monthly in order to use their service. I asked for something to be emailed to me explaining an additional service. The phone rep said, "Not a problem."
Not a problem? I am paying you. I am in fact asking if I can pay you a little more.
Not a problem?
It had better not be a problem. If it is a problem, then you may choose to reduce your problems by simply cancelling all your customer orders.
This phrase draws upon the worst intentions and portrays the utmost disconcern for true customer service.
In replying to a customer query, be it on the phone or in an email, stick with, "It is my pleasure" or "I am happy to help."