Vodacom 4G Poor Speeds

Hi Vodacom, My Mother recently Signed up for a 400 GB Data Package with 20 Mbps Bandwidth and It's Xtremely Slow when downloading from STEAM "The Desktop Gaming Client"

I've placed my Router on The Window Sill of My Home and i'm using 1800Mhz 4G with a HUAWEI B535-932a Router. My Speeds are Absolutely 100% Terrible & **********! 😠😡