I experience the same problem here in Magaliesburg and I DO have an antenna (not an el cheapo one either) and a full strength signal. This problem has been ongoing now for almost 18 months. At least once or twice every single day the signal just drops completely at the tower (NOTHING to do with my connection or aerial) and sometimes comes back within a few minutes, sometimes hours later or the next morning. I have often proven this FACT by putting my card into my laptop during an outage and driving 5km towards the tower in Magaliesburg where I then have a natural full strength signal (unboosted) and gee ... guess what still no signal.
Last night at 23:33 3G and GPRS dropped completely and were not restored until 9:15 this morning after I had contacted the engineers for this area. This afternoon at 5:15pm the signal dropped again and came back after 30 minutes but since it has come back it is not allowing any connections on 3G. Before you ask, the signal strength is FULL strength but not allowing any connections. I am NOT in a high usage area, I have been on 3G since it's inception and in the Networking and Internet fields for 16+ years so I know about settings and I know how the Vodacom system works.
The problem is definitely on Vodacom's side, I never ever attempt to lodge a complaint until I 100% check everything my side. Frequently I am told it is a problem at the CORE, if I hear those words I just want to hurt someone (really). I am quite certain the CORE networking guys get paid nothing short of a small fortune yet we can never seem to go more than 1 or 2 days (max 1 week) before all prior problems return. I've taken this up at various levels with Vodacom on numerous occasions over the last 2 years and sure enough every time I kick up a fuss everyone tries to sort the problem out, engineers are in constant contact with me and in some cases the problems disappear for a few days but they ALWAYS come back.
For the last 4 months the biggest problem has been extremely slow speeds, that has improved to an extent since my last contact with Vodacom, but now the disconnects seem to be getting worse again, classical fix one thing and something else starts breaking ... go figure.
Tonight I am stuck with GPRS only and completely unable to finish mission critical work I had started at 9:15 this morning and have been frantically and constantly working on all day just in case Vodacom had another outage. Sadly I did not make Vodacom's 5:15pm cut off deadline this afternoon.