Sorry Vodacom, but I am not stupid

I have recently contacted Vodacom with a complaint that my subscription (ex VAT) went up by R41.35 (I am still under 24 month contract). After half an hour on the phone, I was first informed that is because my data allocation increased from 500Mb to 650Mb (I have 1 Gb inclusive + an additional 1Gb every month). They then changed the story and I received a reference number (A2-AVMY-GCH110) on Wednesday afternoon while they "will further investigate". On Friday morning, I received an SMS to inform me that the ticket has been closed with the response that Vodacom sent me an SMS on 2 March that the VAT rate is going up and therefore my subs will change. They must really believe me to be an idiot if they think that their pre-VAT increase (and my reduction in data) can be explained by the increase in the VAT. Sorry Vodacom, admit that you are trying to pull a fast one, or that you made an error, but please do not call me stupid.