Isn't this *****ing?

I have a data top-up contract with 5GB monthly which loads on the first of the month. If you run out of data and purchase additional data, BE CAREFUL as in the new month the contract data kicks in first, and only after it is used up, does the additional data (or what is left) that you purchased as a top-up, start being used. BUT here is where they ***** from you: the additional data purchased has to be used up by a certain date and if it is not used up by that date, you forfeit the data not used - this is theft in my view. I have phoned Vodacom about this but got nowhere. I ran out of contract data on 25 Sept.I topped it up with additional data bundle purchase of R289 (5GB) which lasts a month - i.e. till 26 Oct. On monitoring my data usage on My Vodacom portal, I had about 10Gb of data available for the month. On 20 Oct, my contract data was used up. On checking on My Vodacom I still had 4.4GB of data left to use-but here is the crunch-it is only available till 26 Oct so whatever I use up to 26 Oct, I am still not going to have data left after 26 Oct till the end of the month! In other words I lose the data I bought because of the date issue - this is *****ing from me!