Telkom overcharging and too lazy to investigate

I opened a case on 26 June 2020, as I am being overcharged. I took out a contract for a R399 package. I am now paying R649 which makes absolutely no sense to me. The matter was referred to for investigation but closed without giving me a reason as to what transpired with this matter. I have been charged R649 or more since 2019. I need an investigation to be done and to be reimbursed. Can someone assist me with an update in this matter, case number is ***0. The staff at Telkom are very unhelpful.