MTN - Terrible / Non - existant customer service

I upgraded my contract in May 2021 to a Mega Talk package and was assured that the total contract will cost R959 per month. Upon receipt of the first invoice my bill was R2189.65. I immediately contacted the Customer Care Service and they advised me to go back to the store (MTN Brooklyn) and request them to send the contract through. I did that and despite several attempts to address the matter and even escalating the matter to MTN Complaints, on more than two occasions, after 3 months, my bill is still not corrected... I have more than 10 reference numbers and every time I contact MTN they promise that they "now" have corrected the problem until I receive the incorrect invoice again! My monthly invoice is between R1500 to R1600 a month. I subsequently cannot submit the incorrect invoice to my Employer and claim back my cell phone allowance. I am very disappointed and upset with MTN and will never renew my contract with them again...