Missing airtime and a rude agent on the call centre

I have noticed that my airtime is missing, i then called vodacom, they checked if i have any subscriptions that might be taking my airtime, which i have none. The consultant then checked on my profile to check whats taking my airtime. She said that there are calls that i made which i didn't and she further advised me to get an itemised billing statement since we are not in agreement which i have to spent more money on top of what i have already been charged. She refused to log a call or further investigate instead she just put me on the rating voice. Vodacom is just getting worse and worse everyday. Airtime is always disappearing without a reason and worse the agent didn't care about losing a customer. So much of customer service