That's probably the worst kind of thing one can do as a provider.

There is nothing wrong in trying to resolve issues/demands of a customer, if it is within reasonable scale. If they consistently asking for other services, this or that, it can be explained that you are running a business and as such their particular request(s) cannot be met because of their scale. Since its not something that you usually do (and its not within the scope of services you offer), you can tell them it will cost more if they want them.