Cell C Expires Data BEFORE the expiry date

My wife purchased a 100Gb Data SIM on promotion from your Buccleuch offices. She ended up standing in the queue from 8:23 until 16:57 that day to get it. She enquired from the sales person on duty how long the data would be valid for and they responded that it does not expire. We selected this sim for our backup to our DSL line so it really did not see a lot of use. We then went on holiday utilizing the SIM in a normal USB stick modem and I checked the balance at which time I noticed that the expiry date has been set to 31 December 2015. This was 2 weeks ago. I then proceeded to use as much of the data as possible which even on a shared connection and all possible machines and devices connected amounted to 27Gb only. Today I wanted to download big amounts of data to use the rest. Guess what... it is the 31st of December and it looks like the data is gone. All remaining data has been ****** by Cell C! It is not the first time this had happened and this data was not even valid for a full 3 months since the SIM was issued!!