Got it done too and confirm Intex Aqua Fish works with Sonera 4G in Finland.

All i had to do was to change the APN name from "Internet" to "Sonera Internet" and reboot... I also changed the Sim card from Slot 2 to Slot 1 but not sure if that had anything to do with the 4G settings working. Just mention it cause i have seen all kind of strange things in IT over the years...

Now i am happy - who would have know that a 76€ phone can be that good.