Shop-by-phone — called mobile commerce — works in several ways. Smartphone apps and mobile web sites mimic the online shopping experience, downloadable barcodes can be scanned and used like a gift card, chips and stickers turn your handset itself into a credit card, and some retailers accept orders via text message. The underlying idea is the same, regardless: Your cellphone can be an alternative to the credit cards in your wallet. The stuff you buy via mobile commerce is typically charged to a credit or debit card — usually kept on file with a merchant so you don’t re-enter the account number each time — or to your cellphone bill
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