Prepaid and postpaid ARPU is peculiar to the telecom service companies. They offer their customers a variety of options, which break down to either prepaid or postpaid versions. Prepaid service requires the user to pay a flat fee monthly, in advance of using it. This is the "pay-as-you-go" option that can be canceled at any time. Postpaid service is billed monthly. This is the type of plan that may come with a "free" or discounted phone and a contractual obligation to continue the service for a set number of months. It appears that the trend favors the prepaid option. At T-Mobile, for example, prepaid ARPU rose steadily between 2013 and mid-2021, from 28.25% to 37.53%. During the same period, postpaid ARPU declined from 54.5% to 47.61%.