Hi Mikael,
you can order a Starterkit with “public internet access” (it’s a bit misleading, but you need to select LTE-M starterkit in the order process). However, this is only available for testing purposes and not for productive systems. So in our paid plans we cannot offer this at the moment.
In our standard setup you would usually trigger the downlink message via API call (or directly in the portal) and thus the device’s IP does not need to be fixed.
BR
Florian