Incorrect bill

Telkom has been frustrating their customer but I never thought it will come to this, I app**** for a new contract before my upgrade was due as my phone was ******, I was informed that I need to pay outstanding amount of R403 once off, or R80 for 5 months, I choose to pay once off, and I was surprised by an invoice that was sent to me that that amount is 403 per month for 5 months, or R2000, I called Telkom, and they say I must complain at the store where I took a contract, I went to the store and case was registered and they promised me Telkom will call me, no Telkom called me, I called several times and always speak to different people who always promised that someone will call me back but up to so far no one called, And gave me an answer.