Vodacom at it once aggain

I upgraded my data contract to a cell contract online. The plan I opted for was a U Choose Flexi 150 as this was for my husband who is unemployed . He does not need Data. I have just viewed my statement online and Vodacom has loaded the upgrade on a Smart Top Up S+. The U Choose Flexi plan is R 179 per month, the new invoice is for R 309. I have phoned the call centre and was told that they can't downgrade as a discount was put in place. I don't care about the discount. This is YET AGAIN Vodacom who has stuffed up and the client has to foot the bill. I want a refund and I want to be downgraded. As this was what I actually requested.