I think they can just remove the annual plan all together and add a discount that "you get monthly discount after you subscribe for 12 continuous month, and tha

I think they can just remove the annual plan all together and add a discount that "you get monthly discount after you subscribe for 12 continuous month, and that discount is terminated after you stopped subscription". And then there will be no cancellation fee argument. Gyms use this type of discount all the time and don't really have any issues.