I promptly cancel them and then send them a confirmation email telling them how long they can still access the site before their membership expires. I also tell them how they can do it themselves next time in case they couldn't figure it out. Lastly I thank them for joining in the first place.
I believe customer service goes a long way and a few have taken the time to reply telling me how much they appreciate it. It seems to work as I get a lot that keep coming back
