Be careful with U Data Roam at the border states.

I was at Johor customs on Umobile 4G when it dropped me.
I was connected to Singtel and even though data roaming is off I received SMS I had activated U Data Roam RM 10.

I called the helpline and they informed me that as long as your phone is LTE and has roaming. Even connecting to Singtel activates the roaming.

They refused to reverse the charge.

They informed me the only way to avoid this is to manually select the Telco from Umobile 4G, Umobile 3G or Maxis; or disable roaming. Meaning at places where 4G is weak it won't auto switch to 3G or Maxis.

So just FYI not good for border states where your Umobile can drop and connect you to a roaming partner automatically.