Same thing here, I 'just' moved over from telkom LTE - getting consistant 5 bars with them.
With WebAfrica too now, getting 'mostly' 5 bars - dropping to 4 now and then. My download/upload speeds stay good almost all the time from what I've been able to see.
However, I am getting a lot of mini disconnects or big lagspikes that lead to a disconnect, noticeable in the speed tests too (where the download graph has huge dips to 0) it only lasts a couple seconds at most, but it is enough to cancel downloads/disconnect from games/streams etc.
I was thinking of getting an antenna myself, however, surely if my signal is most of the time at 5 bars the antenna isn't going to change all that much? the instability/disconnects are really killing this for me.