I don't. Someone cancelling a subscription does not necessarily mean i've lost them as a customer. The plan is what it is. I'm not into making a hard sale, if the subscription isn't meeting your needs I want to treat you right and get you out of the program. I have a lot of people that are just getting new plates, or a new car. Some leave for a while and then re-signup. Some just don't wash enough to need a subscription and become single-wash customers.
When a subscriber does complain about something, Such as the subscription not working, I do try really hard to make it right by them though. I try and retain them before they say "I want to cancel".
If appropriate, I'll extend their subscription or something to make up for not meeting their expectations.