A mobile device executes an operating system (OS) call manager and an over-the-top (OTT) calling application. The OTT calling application receives a notification for a first OTT call, and notifies the OS call manager of the first OTT call. The OS call manager assigns shared device resources of the mobile device to the first OTT call. The OTT calling application receives a notification for a second OTT call, and sends, to an OTT Telephony Application Server (TAS) without notifying the OS call manager of the second OTT call, a request to switch from the first OTT call to a second OTT call. The OTT calling app identifies the first OTT call as inactive and the second OTT call as active, and allocates the shared device resources assigned to the first OTT call to the second OTT call.