What is the ruling on a communication service that allows a subscriber to talk for one hour for a specific amount for one day, knowing that not utilizing the full duration does not entail a refund of the remaining amount?

There is no objection to that, because it is a specific and temporary benefit. The lessee has the choice to utilize it or leave it. The company is entitled to compensation by enabling the lessee to utilize the benefit. Both parties have consented and agreed, and "Muslims are bound by their conditions." The rent is due upon enablement, regardless of whether the benefit is utilized or not.