Are the people calling you potential buyers of support? [Assuming they are not freeloaders by nature, individuals who might not want your business support, etc]
If they are potential buyers this is an EXCELLENT marketing opportunity. They are calling you for something they need. Converting that into a transaction is a clear path that many callers themselves may expect subconsciously. It's all about positioning and expectation management!
The key thing is to setup expectations, right from before they call, to the number they call, what they hear when they call, about the different levels of support, paid & free, how they can reach the right tier of support for their category, how they can upgrade their support tier, and how they can resolve their problem.
For instance, if you have a support forum + support FAQ, redirect all free callers to that --- AFTER telling them that free support is community supported, with customers just like them providing support.
If they want a specific type of support or customization, or installation support, then direct them to the relevant FREE instruction manual, and tell them that premium support for these is available for enterprise/business customers.
For callers make sure your IVR script takes into account both free and paid users [if you use the same 1800 number, you could also give toll-free numbers for premium support users, and toll numbers for free users].
Your script could be
1. Premium support users: Please enter your support id to be taken straight to our support team
2. If you do not have a support id:
Press 1 for free installation support options [list out website address, forum address, FAQ address, etc.].
Press 2 to buy premium installation support [[ Note the 'to buy' clearly setting their expectation ]]
Press 3 for free post-installation support options [list out website address, forum address, FAQ address, etc.].
Press 4 to buy premium annual support
Press 5 to reach sales
Wherever you list your number make sure it's listed as 'Premium Support Number' or 'Business Support' or something which will influence the caller to understand that this is not free support. For instance you may now have 'Toll-free support number' - which is misleading!
I guarantee if you do this right, you will have more satisfied users and potential customers!
If you want some consulting around this to help you implement this fully, drop me a note - I've been doing marketing/prodmgmt for an open-source based software vendor for a few years. [[ prasanna at wignite dot com ]]