noun
carrier billing; mobile payment charged to phone bill
A payment method where purchases are added to the user's mobile phone bill instead of using a credit card or cash. Common for digital content and app stores.
アプリ内の購入はキャリア決済で支払えます。
In-app purchases can be paid for via carrier billing.
モバイル決済 is a broader term for any mobile payment, including e-wallets and QR codes, while キャリア決済 specifically refers to charges added to the phone bill.
Compound of キャリア (carrier, from English) and 決済 (settlement, payment).