I upgraded my line in August to a cheaper package

I upgraded my line in August to a cheaper package. 500min and 5G and R60 airtime and discontinued the Smart-L line. I have been requesting Vodacom to please update my account balance since September. I currently owe R839 instead of R135. You promised to correct the account and I am still waiting. Contract Smart L line was canceled in August. Instead of resolving this you moved me to prepaid. I never asked to be moved to prepaid. Also i provided you with the correct address for delivery of my sim card. What must i do to be assisted? Very unpleasant. Please can someone who knows what they are doing assist me. I want my correct line restored asap. I have all the emails confirming which line i upgraded to.