Incorrectly billed by TElkom

I am not happy with Telkom billing system as i have been in this path before and took long to be resolved. i have cellphone contract with Telkom and i pay R339 per month. in November i missed my debit order payment and i was i paid in few days days knowing that i will have to pay the addition +- R201 debit order fee. December the 23rd my account was debited with the R541 and i was happy and accountable. on the 20th this month i received an payment SMS from Telkom showing R541.70, i called Telkom and the consultant said he has the incorrect Debit order fee and the the error was fixed and the amount that will be deducted on my account with R339. then i reserved enough money for the debit order to go thru surprisingly i received the the reversed debit order SMS from my back, when i go to the app i see that Telkom was still the incorrect R541.70, hence the amount was insufficient. i will not pay Telkom till they fix my account and my question is who will be liable for the reverse debit order ? while it was incorrectly billed knowing Telkom.

i have been in this route with Telkom before and my case was resolved by ICASA. Telkom has poor service.