Migration to lower package

I have migrated my contract from a Smart M to a Smart X'S which I received email notification to confirm the migration would be in effect from 31/08/2015. I noticed at the end of September that I was still getting billed the same amount which should of been less because of migration. Once again for the second month I am now being billed the same amount for the higher package which I migrated from to a lower package as I couldn't afford the amount anymore. I called three times between then and now and spoke to numerous people who confirmed the migration was active yet I am still being charged the higher amount. This has now resulted in me being stuck in financial situations. I honestly want to cancel my contract because this is costing me money that I don't have even after changing my contact so that I could afford it. So frustrated and annoyed with Vodacom.