Frustrated with Cell C

I received a call from this number *** about account being in arrears. Siphiwe Mosime requested that I go to Nedbank to pay the amount before i can cancel the accounts. He could not email me the bank details as the 'system' was down I have been trying to get hold of Cell C to clarify the issue as the account was for a modem and is not in use anymore...I have tried sending a message from the website, the customer service email address not in use anymore, I called but once i put in the number linked to the account the calls just end...HOW DO YOU CONTACT THEM!!