Telkom's whole "argument" makes no bloody sense anyway. The only reason data could cost more than voice is due to DSLAMs, but those are sunk costs anyway that should not factor into the cost to consumers!
But remember, this is a company run by dumb c**ts who buy MultiLinks for R2.8bn, lose an additional R5bn over the course of its operations, and sell it for R350m two years later. If Telkom's statements about line subsidies aren't blatant lies, that R7bn could have covered their subsidiary costs for YEARS and they could have passed savings down to consumers, thus growing their subscriber base.
I didn't even take Economics 101 and I know more about customer management better than Telkom's CEOs. Isn't that pathetic?