Our telco data line (MAXIS, CELCOM, Digi, U Mobile, YES 4G, XOX, Yoodo and etc.) is bad and unstable, there is only 50% of chance the line is really congested in our areas.

The other 50% of chance is because someone is using the phone signal jammer to block our line so that we cannot use the data to online, and even call.

When we enter a building or our house, if the 4G line suddenly drops a lot, or even drop to H/3G until cannot online, but the line will goes back to 4G normally after leave the building or outside our house, then we can sure that someone is using the jammer to block our line.

If I am not mistaken, it is illegal for those who do this according to MCMC.