we will save you money (costing me R100 more) Lies lies lies

On 9 June 2021 I got a call from *** offering to upgrade my contract based on the usage and that it would cost R30 per month less (current bill is about R1700). With the great offer I said yes, This month I got a bill for R2600.00 (R1000 more than normal) I logged a call with vodacom on the 09 July 2021, they revered the "upgrade" but did not credit the previous invoice. So due to them lying i will be out of pocket by R1000 this month and they are debating if they should credit this. Terrible service and horrid sales people. Thier lies on the call are costing my R1000 more in a time like this pademic where every cent counts.