I've got a subscription service with a free tier. Initially, the free tier was far too generous. We've since significantly lowered what that free tier provides. However, we had grandfathered in people already on the free tier.
What are some strategies for moving people from a free to a paid tier, when the two tiers are nearly identical for these users?
I'm looking for some more creative solutions than simply ending the grandfathering of the original free tier (which I imagine we'll have to do eventually).