Here's what Basecamp did:
* on their monthly receipt email, they have a link directly to the cancel option.
* They remind you to get your data on the way out, and give a link, right there, to go get it
* They give you your data
* They cancel straight away, and ask if it's ok to survey you (optional).
After reading the book It doesn't have to be crazy at work (https://basecamp.com/books/calm ) I understood the mentality perfectly. I wish them all the best for their product.