Furious and disgusted customer

Today I've looked at the My Vodacom App to see if they've calculated the money I'll be paying end of August since I've made a few changes on my 2 contracts. Only to realise that the total is so high I've called in today to confirm what I'll be paying for my Fibre, the lady I spoke to Thando confirmed that she can see the quote was discounted to R599 for 12 months but the discount wasn't app****, hence my bill is sp high. She also mentioned to me that the guy made it effective from the 18 July. Who does that?!? I already had a current contract, so he was supposed to have done it effective from 1 August!!! He didn't even mentioned it to me that he'll do that, because if he did, I would've told him NO. Can someone please rectify this. This is so draining that whenever we renew contracts your salesmans tell us a different story and do completely something else. This is really nonsense!! This is ******** practice. I don't understand how you guys get away with this year in and year out. I guess because not everyone complain about this. Please fix this before your statement date. I refuse to pay pro rata for a survice I didn't agree upon!!!!