Use the freedom that the USB cable connection gives you to find a optimum reception spot.
Remember, it operates via wireless technology, so depending on the current load on the tower you connect to, your speeds can vary greatly from period to period during the day. Also remember that in SA, the term, "best effort" is very dearly beloved of our Service Providers" it gives them an out so big that you can drive a bus through it sideways, and mot have any fear of bumping anthing.
They all advertise LTE, as if they can deliver it, when they still cannot deliver 1/3 of the speed of a 3G connection's thru put capability.
The fact that their towers are overloaded and congested to hell an gone does not bother them, as if we are not paying for the most expensive data in the world.
So don't have expectations of getting wonderful speeds.