Contract cost went up with R50.00 - 14% increase! Vodacom app shows less.

My contract amount suddenly went up with R50. 00 out of the blue. My math may be a little of but it looks like an increase of 14.34% (R348.50 to R398.40)! I phoned their call center and asked about it - only to be told I have been informed via SMS about a price increase, but the increase amount never seems to have been communicated to me. The Vodacom app however displays my bill as R348.50 while the invoice is R398.50. I asked about this and the consultant admitted on a recorded call, and repeated it, that the Vodacom app is not correct in regards to the billing amount. What is the use of referring customers to the app when their own call center consultants admits its not correct? Did I not sign for a certain amount a contract and now they randomly increase prices? Call Centre agent = Frieda Saohatse, time of call = 08:16, date of call = ********** 3, my account number = I **********