Overpaid account gets extra transactions so that I must pay more!

I have my Multichoice statement in front of me for period 05 Sept17 - 04 Oct17, my closing balance is R60.51 and on the age analysis it is under the "not yet due" block!

05/10/2017 I paid R450 (As USUAL) as I always try to keep the credit balance! Then I was disconnected and them telling me that I am DUE on my account....(Uhm R60.51 due less R450 payment = R389.85 overpaid) so I had to pay and additional R175.26 on 16/10/2017 to get it RECONNECTED...at MY cost! I was not even supposed to get disconnected! Now I am R517.57 due on Nov, which is also incorrect!

Who added that transactions to our account in October and why?? We were on the phone TWICE with the call center for more than 30min each and they recon my billing is R500 p/m and I only pay R450... but I only do that because I KNOW I have a credit b/f. Extra transactions was added to our account on purpose to disconnect us and making us pay more!

I do not know why we bother with this dishonest company.