A method includes providing a first payment account that is issued by a first financial institution and enables an accountholder thereof to make payments at merchants via a closed-loop payments network corresponding to the first financial institution and mobile person-to-person payments using the payment account. The method includes enabling a second payment account that is issued by a second financial institution to be electronically linked to the first payment account and used as a source of funds. The method includes providing a mobile operating system and enabling a plurality of merchant-specific payment accounts to be associated with a mobile communications device having the operating system. The method includes determining whether a merchant-specific payment account that is accepted only by a particular merchant is available to the accountholder via the mobile communications device and receiving a fee when the first payment account is used for a purchase.