INFORMATION NOT PROVIDED

I bought 1 Gig of Data on the 18th Dec 2015. On the 16th Jan I had 6 hundred and something mega bytes. On Sun the 17th Jan 2016, I had 0 balance on my account. When I called the call centre I was advised that I forfeited my data. Apparently after a month you forfeit what ever data left on your account.....that simply means it is a waste of money to get the 1 Gig. What's annoying is that you are never told that you will forfeit your data if you do not finish within a month. When I asked the call centre agent why don't we get SMSes advising us, he told me that, they do not do it. My question still stands as to why aren't we not advised or reminded that if we do not use all the data by a certain period then you will forfeit it??? I am very disappointed!!!