Misrepresentation by MTN

I was on the MTN Mega Talk XL package and was running out of data so went into the MTN Shop at Century City Cape Town, about two months ago, where a guy sold me a migration to a Sky Silver package which cost R1000 more per month. Its advertised as 50G anytime data but actually the data was split 25G anytime and 25 G between midnight and 5am. This was not explained to me as I can assure you i'm not waking up at midnight to use data at 51 years old. So when I went back today to ask why the data was being split 25G on the 3rd of the month and 25G on the 18 of the month, the lady explained to me that I should and doesn't know how I even got migrated to that package as that package can only be taken out when you sign a new contract or do an upgrade from inception, not to migrate to. She then also explained about the 25G midnight thing. She said she could put me back onto my original package (R1000) cheaper, but that it would cost me R100. So I asked to speak to a manager who said he was sorry and that the gentleman concerned was not at work today but clearly needed more training. Was also told that the old package was only going to kick in at the end of September, so my question and major complaint is that as a consumer I should not be required to fit the bill for the different in the old and new package when it was wrongfully sold to me by MTN staff.