Downloading/Buffering stops after a while

My 4G provider is Optimus, I am pretty sure they did mention something about having a bandwidth cap and they would slow my internet down after I reached it, either way, they did not give an exact value and the Speedtest gives the exact same value from the time I got it. As I said, they did not mention any value for the limit, and if there is a limit, could it be something as low as a value around 4GB (Around what I have downloaded in 2 weeks)?



I got the 4G 20 which says Unlimited for bandwith.

EDIT: Thinking about it, a month has just begun and I still have the same problem. Also, browsing the website, there's nothing about a bandwidth limit.