Don't charge me for your mistake

Around the middle of November I used the Vodacom iPhone app to order a once-off data bundle for my sim. A recurring bundle was activated instead. I called the helpline immediately to have this rectified. The operator activated the once-off bundle, and said that the recurring bundle could be stopped, but it would only take effect in the new month. This was unacceptable to me because it meant I would be billed for both. She said she'd put in a request for it to be removed. I got no feedback. I called back a week later for an update and explained the situation again. Same response, no feedback. Now sure enough, both items are appearing in my statement, even though this data was still untouched by the end of November. I do not accept being charged for something I never asked for and never used.