They can cancel the prior tier or bump up the price on renewal though. This is the problem with subscriptions, you become complacent and accept incremental changes until you finally notice that you’re being rinsed.

And actually some subscriptions can include unilateral price increases in the contract (a subscription is a contract) with early termination fees. It just isn’t commonly done because word gets around and you will lose business. You typically only see this in predatory industries where there are few alternatives and the service is necessary, like local waste management.

If the contract is unfair enough you can usually escape it in court or arbitration, but nobody wants to go through that.