Well to get started you would need a router with sip build in. I know that Telkom supplies the B315 with their fibre setup. So then it's very easy by simply adding Mweb Talk sip details into the router and you are done.
If you do not have a router that does not have sip build in then you can get one of these very interesting devices.
https://www.aliexpress.com/item/Bra...phone-adapter-SIP-VOIP-Phone/32726080515.html
These devices connects like what is build into the B315.
Pro's of using Mweb Talk is paying No monthly fees but getting a local did number for free.
Con's is the call rates are not the best. @75c per minute to cellphones it's not a good deal but not horrible either.
If you really want cheap VOIP calls your best bet is
https://www.discountvoip.co.uk
Call rates of 8c per minute to any network in SA anytime. Call quality is okay but rate is unbeatable.
Con's with that service is there is no incoming calls. You can however set the CLI to be your cellphone number or even a land line number or a VOIP number which is really cool.