Yeah, our Dash class documentation is hidden inside these forums. Using the Dash class
Since you’re using embedded Linux I would recommend a Huawei E303 Cellular USB Modem over the Dash. Right now the Dash cannot accomplish what you want but the E303 can. Plus you could probably find some tutorials on the web.
You can purchase the E303 from our store Cellular Connectivity for the Internet of Things | Hologram