******* random debit with no notice

My 2 year contract is coming to end in a month. For the 1st time, in November, my debit order bounced while I was travelling because another company *******ly debited me and left me without funds. When I got back, I received an sms from Telkom asking for the missed payment, with no email address, phone number or bank details to use, which I made for R273 on 6 December. They also debited me for R273 on 30 Nov for the new month, so it's quits. Nothing outstanding. Then, yesterday evening I get an sms stating that a trace alert had been placed on my name by Telkom for an arrears of R752,57 which I ignored because it asked me to click on a link to pay. Then, This morning, I see that Telkom had debited my account for this amount! I've been awaiting a call back from them since 07:28am! Also, AFTER making this debit, I get an email from their debt collection department for this amount. No notice, no details for what it is as the amount is so random! I will not be renewing my contract for sure!