It's not sleazy to end a sweetheart grandfathered deal that they only ever continued out of the "kindness of their hearts" for the customer's goodwill. If I move into an apartment for $1,000 a month and a year later when my lease is up my landlord allows me to stay at $1,000 a month even though the new rental rate is $2,000 they still can decide in 6 months if I'm throwing loud parties every month that they aren't going to keep me on my old less expensive lease. They can say "You know what, we're not interested in renewing your lease." or they can say "If you're going to be eliciting complaints regularly from your neighbors for noise you're going to have to pay the latest full monthly rate for a unit of your size which is $2,000.
"Maybe it's technically legal but it's still sleazy" applies as much or more in my opinion to being given an unlimited *phone* plan and then using it to substitute a fixed land-line internet plan at the latest network speeds even though you originally probably signed on for an unlimited 1mbps connection.
Another good metaphor would be you move into a pet-friendly apartment building. But you have a dog that endlessly barks. They can decide that while they are pet friendly *your* pet is not welcome and choose to not renew a lease. To be even more accurate it would be like moving into a pet friendly apartment, the apartment building being sold to a new owner and pets being banned, but anyone currently renting can keep a pet indefinitely. A year later your pet turns out to be a nuisance and you are evicted because your pet is loud.