No Roll-over of un-used Internet data

When you purchase an Internet bundle you are offered 20gb day and 20gb for night. First of all, who sits up all night trying to use their 20gb night data? This is an advertising ploy. My biggest problem is that when you have used all your data, Telkom is very quick to shut you off. However, when you have not used all you data (day or night) they do not roll the unused data over. I understand that they are now doing this for mobile phones, but what about Internet users!!! I will not renew my contract where the provider is Telkom they are an absolute rip-off. Anywhere overseas, the monthly payment is very small and the users have unlimited data...... my BIGGEST grip is the fact that they do not roll over unused Internet Data. Wake up Telkom (another Zuma????)