BAD SERVICE

I was called by mtn agent on friday 29 that my mtn account is in arrears with R389.00 that i didnt pay my account in April and May, i send them my bankstatement to show that i paid the account on the 20th every month i even got sms from mtn that they received my payment. i think 4 call center agent called me telling me that the money was reversed and i didnt. Yesterday i got a call again that i owe R210.00 , i dont know since when im called to be reminded about the installment on the 2nd as i alway pay on the 20th. They also told me that i receive more data bundles that is why i must pay 210. my intallment is 189.00, i didnt get any extra data bundles i only got 100mb, so please tell you agent to stop calling me as i always pay my account on time and never been on arrears, the lady was so rude and telling me they going to close my account if i dont pay extra R11.00, im not going to paying any extra R11 cause my installment is 189.00. FIRST WAS MY INSTALLMENT REVERSED FOR 2 MONTH NOW IS EXTRA BUNDLES, I THINK I MUST GO TO ANOTHER NETWORK CAUSE REALLY I CANT TAKE THIS NOSENSE ANYMORE, ONCE MY CONTRACT IS FINISH I WILL GO TO ANOTHER NETWORK