phonecard
A small card, usually resembling a credit card, used to pay for telephone services. Used prominently but not exclusively to debit at payphones such as Danbooru post #3972756.
Some cards come decorated with various prints or characters for collecting purposes.
This tag to both the card itself, as well as refers to the design of such element ala dakimakura (medium).
Japanese name: テレカ (teleca / tereka) or telephone card.