Unable to access any account details

I have been getting very high data bills from Vodacom. I've been trying to access my account to determine where it's coming from with no luck. They send me monthly statements in an .efa format, which I have been unable to open since it started. I searched the entire internet and nothing that I have downloaded, seems to be able to open the file properly so I can view it. I've also tried to log onto their website, but cannot remember the password. When I click on forgot password, it tells me my number is not registered with them. When I try to register, I'm told my ID number is already registered on another account. I have phoned Vodacom about this NUMEROUS times, and they merely tell me they will log a call, give me a reference number, and then I never hear from them again. This has been going on for months and I simply cannot access any account information.. giving them the opportunity to change me ANYTHING for my data usage and not having to prove anything. How are you supposed to manage your account without being able to access it. And Vodacom simply has no motivation to assist me in any way. Shocking service !!!!