I talked to an Enterprise rep about this when I picked up my most recent rental car. I too, get this call after every rental. The call actually comes from a mystery shopping agency that collects the feedback for them. So, if you feel inclined to comment on service, whether good or bad, take the survey. The feedback the agents receive from customers determines their performance review, and can affect whether or not they get promoted.
They called me in the afternoon. Asked for me by first and last name. I said 'this is him', awkward pause then they hung up. Other people are mentioning it's Enterprise. I did rent and return a car to them this week.
I had a rental this past weekend from enterprise through the dealership. Once I return the car Enterprise was closed. However, they called me on Monday to make sure everything was OK. I told them when you give someone a vehicle the tank should be full already. We returned The vehicle on full. They say they will make a note of it to ensure it doesn't happen again. You seem that this number was a follow up to the previous call. They seem to be legit.