RV50 Sierra Wireless AirLink modem should require only entered APN in device to work with a Monogoto SIM card.
To change APN settings, please do the following:
1. Login into your modem
2. Go To WAN/Cellular and select Cellular
3. Click on SIM Slot 1 Configuration or SIM Slot 2 Configuration (depending in which slot you have inserted the SIM card)
4. Enter APN and save changes
Example showing APN data.mono used in RV50 Sierra Wireless AirLink modem