Vodacom False advertising

I upgraded my contract online with Vodacom last year .

Signed up for a R199 20gb data package ... R199 being the price I agreed too.

I April 2019 I queried why I was paying more ,no answers .

December I inquired again , was first told that it was the Vat amount , which was totally incorrect as forwarded to the accounts department.

The accounts department then just sent some generic sms as the final reply , to the data sim to say that there was a price increase to contracts in April 2019 , due to out of bungle charges , which was new legislation I guess.

It is a Top up contract , if no data it stops automatically , why bill me more .The same contract was still running till November last year at the original advertised price.