Double billed

I upgraded to 5G service from 4G & I paid upfront for the month the was told I wouldn’t not be charged by the sales consultant as she canceled the previous plan. I was charged R479 on the 1st of December and I spoke to another consultant who apologized and said it would be rectified and the billing department would contact me.. I followed up today the 5th of December and another consultant is changing stories.. I am very unhappy with the service as their are quick to call for sales but not for customer service