A method and device are described for maintaining software components in a portable electronic device. The device includes memory storing software components executable from the device, with associated pairs of logical storage partitions for storing different versions of the software components, a data interface for coupling the device to a host computer, a contactless interface for receiving payment token data from a contactless payment token, and a cellular network interface for communication of data over a cellular network. An upgrade process is initiated when the device is coupled to the host computer. Data including a different version of at least one of said software components is received, installed and executed to initiate a payment transaction with a remote system. Payment token data is received via the contactless interface means and transmitted to the remote system.