@AlexOnTour 

Hi，did you enable roaming service for your SIM card? please insert the same SIM card into your smartphone when you are abroad, then check if internet works fine on the phone.

If it doesn't work on the phone either, please contact your ISP for help.

If it works fine on the phone, please check APN profile settings on the phone, and compare it with the MR600 APN settings, please note that when the SIM card is in roaming status, the phone or router should use the APN settings of the roaming ISP instead of your original ISP.