cell c incorrect billing & Very bad service

Phoned cell c for a data contract that was advertised for R399, 20gig during the day 20gig after 12! Call centre agent confirmed price over the phone and that all was inclusive for R399, as all calls are recorded as well! Received my 1st invoice and was billed for the modem and billed for the data!!! R1285 invoice i received!!! I phoned to sort this out on the 10th of November and since then I have spoken to -10 agent all saying it will be sorted out in 2 working days!!! Cell c is a joke and all the agent are very useless!!! I am still waiting for this to be resolved! I phoned my bank and reversed the payment! Still no feedback from cell c!!! After a month and a week!!??? Oh and just received my invoice for December...guess what incorrectly billed again!!! Cell c is useless!! I regret getting a contract with them!! This is the 1st &amp