Samsung Galaxy S4 (SHV-E330K) Korean Variant - 3G / 2G Network Problem

[ScyberMhaster]

I have a Samsung Galaxy S4 Korean Variant. I live in the Philippines, and I believe that this phone is unlocked because I can use my SIM Card to it (Globe Telecom - Philippines). Now, my problem is when I turn on Data Network on 3G / 2G. Whenever I turn it on, on 3G mode, not LTE, because the area was just covered by 3G, I notice in the notification panel that instead of seeing Data Network, I see Data Roaming. So, there's no way to turn off my data mode. And when I go to the Messages, there is a warning that says 'Roaming... charges on receiving text... etc.'. And on the notifications, when I pull it down, it says 'Current network: Globe (51520)' something like that. And when I click it, I will go to Global Roaming in Settings. And sometimes, there is a signal drop, and sometimes it says 'Insert USIM to connect to etc.' or ''Insert SIM Card to connect... etc.' but on a couple of seconds, there comes again the signal for my phone. However, if my phone connects to LTE network, it works fine.

Samsung Galaxy S4 Korean Variant
Android 5.0.1 Lollipop