Uncapped contracts are a blatant lie

I had signed a 24 month ADSl contract with Telkom on a special they had for R599 uncapped wifi. Every single month from month 1, I received and invoice stating that I owe more which meat I would have to top-up with an eft because the debit order which is obviously the same as my contract is not enough. Eventually after many confusing telephonic explanations I went into a telkom branch where the agent could not explain where the extra charges are coming from but then advised me to increase my debit order the the R806 they usually demand. From the first month after debuting my account with R806, my invoice continues to reflect that I still owe almost R200 over and above the R806. So now I must continue to add R200. Thus a R599 contract a month is now costing me R1000 a month. I am considering contacting the National Consumer Tribunal.