Being billed for Telkom's faulty systems, it seems!

For the past 2 years I've had a R149 router contract with Telkom and a month after taking the contract - I set my limit to R0 should my bundles deplete. Suddenly, out of no where - I get debited R650. The first time I was told the limit is not supposed to be set at R0 it should be R1 cause it apparently trips and automatically sets the limit back to R500 (so I paid for Telkom's faulty system). So the second month it happened, the limit of Telkom system was R1 but still I got debited R650. So on their system it apparently says I only set the limit to R1 on the 24 August '18. Beginning of October I still ****en got billed R650 and they cannot credit me because they send me messages (I never received) to say I'm on out of bundles rate.. and I suspect they send me messages to the Telkom router sim.. I'm so ****ed!! I want my money back ?