I would guess it can end the moment either party wants, unless a length was established. At the end of the month or year you’ve paid for, perhaps with a minimum notice, would make sense. Otherwise the provider can refuse to let you stop paying, citing the contract.

Every contract has that, either party can exit the contract under normal conditions. You can cancel your Netflix subscription with a short notice period. They can do the same. They use the notice period as grace period for you to accept the new conditions. You accept a new contract with new conditions.

I negotiated my mobile phone or internet contracts again and again, to get better deals. I threaten to leave, they throw a bone. Because they know I have options. Providers who know you don’t will squeeze you however they please.