This application describes provisioning a secondary electronic subscriber identity module (eSIM) to a wireless device to access a cellular wireless network of a mobile virtual network operator (MVNO) to supplement and offload from a cellular wireless network of a mobile network operator (MNO) that provides cellular wireless services to users of the MVNO. Provisioning of the secondary eSIM can be triggered after i) boot up of the wireless device or ii) insertion of a primary SIM/eSIM that provides MVNO cellular service access via the MNO cellular wireless network. Provisioning can be anchored by an MVNO entitlement server or by a manufacturer device services server. Provisioning can also be triggered by the MNO cellular wireless network after attachment of the wireless device. Authentication and authorization of the wireless device to obtain the secondary eSIM can be based on the primary SIM/eSIM or on secure communication with the manufacturer device services server.