Am i being scammed by BSNL?

I am using BBG Combo ULD 1350, 4 Mbps upto 20 GB, 512 Kbps beyond 20 GB
I stay in Patna, Bihar

However i am having severe problems with the speed.
For example, i pinged store.steampowered.com
i got Average ping of 530 to 560 ms

My speed test result-
*www.speedtest.net/result/1655099831.png

How do i know if i have crossed my 20 gb limit, because i never use torrents or download huge files...