I have same problem but mine is samsung s7 edge SM-G935S which is bought in korea and already used in indonesia smoothly with my provider. But i can enable or activate the roaming because it is locked by korea permanently as i can see it can t be manage bybself and then i tried to install firmware indonesia SM-G93FD. The problem is the usb driver, in samsung s7 edge doesnt work with version driver i tried but it is work on my samsungnote 4 that is as same as i buy in korea both of them.
