It is sometimes useful to compare the differences between an internal help desk and a customer hotline to the differences between the a full-service and a fast-food restaurant. Like the full-service restaurant, a customer hotline will provide you almost anything you ask for (within reason, of course). On the other hand, you are more limited in what you can get at the fast-food restaurant. Granted, it is likely that you can get your hamburger without ketchup or pickles, but that’s about it.
The key here is that you’re providing fair quality at a fair price. This success of fast-food restaurants such as Burger King and McDonald’s are clear indicators that the customers are satisfied with the service. However, it is unlikely that either chain would survive very long if they decided to increase their prices to a level comparable to a full-service restaurant.
In essence, the same thing applies to your help desk. If your customers (that is, the users) are notpaying as much as they would for external support, they are generally satisfied with the level of service. It is simply a matter of economics that you cannot provide the same level of support that you could for paying customers.
However, my experience has been that customers who don’t pay for support are often more demanding than those who are paying for it. This is due primarily to their not understanding what the limitations are. This is because the limitations are rarely spelled out for them. When I worked in support, we provided 30 days of free "installation" support. However, the customer was never told what "installation" really meant. I often got calls where the user was having trouble installing a third-party application. Well, the word "install" was in there somewhere.
On the other hand, your users might actually be paying customers. There are organizations that have broken down each department into separate business units. In general, each business unit is a separate financial entity. Each time services are requested, the requesting department is "charged" for the service. In such cases, the customer (user) might be in a better position to make demands on the help desk.