Short answer: They are the best !
Long answer:
2 years ago, I gave up my landline and ported to Vox. The porting had a few hickups. At R25/month, the pricing was OK, considering they credited me 6c per minute for incoming calls. But the call quality was poor and their website is very unsophisticated.
When Axxess launched their product, I tried to port to them. But they wanted an "authorization" letter from Vox, which I don't think is necessary (reasonable).
Then someone on here recommended Fresh Phone. They said they need an invoice from Vox showing my 012 number, which sounds reasonable. The Vox invoices didn't have it, but I submitted emails from Vox showing that the 012 number is linked to my account. And Fresh Phone accepted them.
The Fresh Phone website is also very nice. For example it shows the latency. And it has examples for setting up popular routers.