I think SMART already implemented data capping and throttling.
For the longest time, I use their 3g service to watch sports livestreams. I can watch it with decent quality. Speed is faster than our office connection even if I am a prepaid user.

But this year, connection speed if crap. Yesterday, I cant even connect to google.

Since I my phone is prepaid, I am thinking of buying several SIM cards just to increase the cap.