Different standards

I have seven lines with vodacom and have been a loyal client for many years. One of my lines is a top up line which I got specifically because it is supposed to assist in monitoring and managing costs. I just got an account for R32742.75 for January and the February account is at R9000.00 already. This is not supposed to happen on a top up account. I have another top up line and once the all data and talk time is exhausted, I have to buy extra so I never end up having to pay huge accounts. I also get text messages alerting me when I am close to having used all data and talk time. However just on this one line none of the mentioned actions are taken by vodacom. Vodacom is applying different rules to the same types of accounts. On the one line I have complete protection and on the other I end up having absolutely no protection. This practice of different standards and rules is unacceptable and at the expense of the clients.