Vodacom Price Increase on a 24 month contact

Dear Vodacom,

Please note that on the 26/03/2019 I took a 24 month sim only data deal contract of R60GB per month for R349 at your shop in Greenstone but to my surprise when I check my invoice for April is showing that i'm going to be debited R369. Today the 09/04/2019 at 14:26 I called your Customer Care line and I was assisted by Gugu Nkosi who told me that my contact subscription has increased which I totally disagree with cos ever since i had contracts I never had of a subscription increasing during the 24 month i signed up for. Please assist.