The problem Telkom have is that it got a lot of legacy infrastructure, which also need upgrading, and users/businesses to be moved.
Same goes for MTN and Voda.
8ta and CellC have fairly new networks, so it's easier to upgrade.
Not so, MTN and VC have been continuously upgrading their nodes. I actually think they have more capable infrastructure than both cell c and 8ta, both on the core and RAN side.