Tax

I took a contract phone (M2 Aqua Sony Experia ) on-line with Cell C on the 25th August 2015 for R227 a month. Since it was towards the end of the month, I was billed less than 20 bucks which was okay. On the end September 2015 the bill went to R280.59 and I called the customer service for an explanation and was told that it was pro rata and stuff and it was once off thing and my next bill will settle to the R227 which was advertised. To my horror again, the bill is now R265 on October and I called again, they said it was tax. I really don't understand this because when I took the phone I was told that it will be the amount that phone was advertised and nothing else. So it means that I will be billed for 32.54 tax each and every month ? What for ? Doesn't the phone comes with tax and others things covered when it is advertised. I am really not happy with this. This is pure ****************.