There may be a few instances where the customer had a bad experience with your company. Consider that call an opportunity to fix the situation and turn it into a positive.
If customers are not calling you, you should be calling them. The nature of these calls is to stay connected and build the relationship. Plus, if your business has changed or if there is a special deal that would be of interest to customers, this is a perfect opportunity to share that information.
Don't start the calls with the sole expectation of generating revenue, but if you happen to rent something in the process, then it becomes a bonus. You know that at some point that customer will have a rental need and it's important to stay top-of-mind, so he or she will contact you for that need.
Outbound calling requires additional skills and discipline. Many of your inside sales coordinators do not have experience conducting these types of calls. With an organized approach, this can be a very effective initiative that will benefit everyone.