Cell c upgrade not done but being charged for!!

I upgraded two of my children’s contracts in august from 10GB top up to 30 gig top up, I was charged the new upgrade price on the 15 August but both my children did not receive their new gig benefits. I have called cell c countless of times to try get this resolved but from them not being about to hear me (considering I’m with cell c calling cell c and they struggle to get connection which is even more frustrating) I keep getting told my contact is a 10GB despite me telling them I’m already being charged for the 30gig!!! I get no joy at all no one is able to sort this out. Now I’m stuck paying a damn contract I’m not getting benefits for!