IMHO.Did u set the APN as TPG? (Samsung default is internet)
Did u use it in Singapore for at least 48h straight before leaving and SMS to 1218 to check if it's roaming ready? (Mandatory requirement)
Are you able to find an iPhone user, setup the APN and connect, and see if the device change from "Carrier XX.X" to "Orange France XX.X"? And also connect to the roaming carrier?
(If the sim card doesn't change to Orange France after trying to manually connect for at least 10 mins, means it's not roaming ready. Don't bother using SIMBA SIM for this trip, it won't get fixed until you're back in Singapore.)
Simba ask me almost exactly the same thing.
It is useless because I can roam to Malaysia and faced with cannot connect in Heathrow and JFK.
To me, cannot connect means the roaming telco reject.
If iPhone can, means compatibility issue.
Will Simba not sell you the SuperRoam plan if it is a compatibility issue ?
Probably sweep under the carpet.