So after 20 years of contract I have moved to prepaid 6 months ago.
here's my experience so far:
I was on a month to month contract after the 24 month rollover, was probably spending R450 per month.
Everything that i had accumulated was available for that month and then disappeared to their bottomline - you bring nothing over.
They will try upsell you...
Since I'm often near to wifi and I hardly use voice anyway these days with whatsapp calling, prepaid was a no brainer. I'm ad-hoc buying 7.5Gb for R99 and R20 airtime. Even though the data doesn't "expire" anymore, they're appealing that ruling or whatever, so it defintiely does.
I now have to manage my account from the app. it is painful. when it runs out, it just runs out. No notification, and you have to work out why the interwebs on your phone is gone. Trying to buy more data when you are out of data (or wifi) just takes forever. You can either buy from a credit card or the "wallet". the banking often hangs. I have looked into the 'wallet', but it appears to be some attempt to get users to have vodacom as their bank. I don;t need another bank account thank you, but it might be a necessary evil.
What really hacks me off, and got me to write this, is voice. I'd like to be able to use my phone to phone people. yet the voice balance disappears. I am convinced of this, and can track my call records. I'm only buying R20 at a time, normally to go an make one call to an office/landline. and then a week later, it's back to R0. therefore nervous to load R200 and see what happens. As we stand now, I loaded R20 on 26 august, and made 3 outgoing calls. 1m50s, 0m13s,, 0m3s..
tl:dr
I'm saving money on prepaid, but it's a hack to manage. especially when it runs out.