Billed for data without consent

I signed up for the Telkom SmartBroadband Wireless 20GB deal for R 299. In September, I was debited R 299. In October, R 299. November, this amount suddenly changed to R 522.45 because I exceeded my spend limit. After calling in to the contact centre, I confirmed that my spend limit is R1. So how did I exceed it?? Whenever I top up to buy additional data, it is always paid for with my credit card via the Telkom app. Please resolve urgently, and credit the R223.45 to my account with immediate effect. I spoke to Kutlwano Moloi who was not very helpful. When I asked to speak to her manager, she said that they are not allowed to divulge such information.