Useless online billing facility

I have tried on numerous occasions to access the Vodacom on-line billing to assess the status of my bill and the stupid Vodacom facility restricts me only to access my prepaid number yet I would be using the log-in details for the contract number. I have been previously billed amounts in the range of R1,500 yet I am on a contract that should not cost me more than R600 despite minimal use thus I need to proactively manage the account going forward. The on-line billing service is pathetic.