billing different from agreement

I have a problem, i took x2 phones (huawei nova y90) on contract, the initial amount excluding insurance was R505, i received an invoice from May and it was R2,454.25 and an invoice for June which is amounting to R 3,453.28 in total including my iPhone contract, the number *** that is supposedly causing the hike in contract is as apparently is on a free plan, firstly I have never asked for this and secondly why would want to pay over a thousand rand for a sim card that I am not using? I have queried this multiple times and with no luck i have been promised call backs after discussion with the manager and still no reply