Cell C - Whatsapp Bundles - Unfair

Complaint with regards to R15 WhatsApp Bundle. I have been gifting WhatsApp bundles to both my boys for a very long time every month from my Cell C account. When you purchase the R15 WhatsApp Bundle it states: WhatsApp Bundle gives you unlimited chats for 30 days at R15.00. Now I have had to purchase 3 bundles for my 1 son in the last 3 weeks. It keeps on going off and giving him an error message of "you have reached your fair usage limit please reload new data to continue" When I phoned the Cell C call centre I was told that the WhatsApp bundle is actually a data bundle - it used to be 1GB and in the interim it has changed to 600MB. Now this is false advertising if the message you receive clearly states "unlimited". When I spoke to the call centre the lady I first spoke to was so board with my call and she just did not care about my question...I insisted to speak to a manager he was open to my problem but all he could say is that they are in the process of changing their message from "unlimited" to whatever amount of data it will be...which I don't believe cause they will have millions of customers complaining about it...that is going backwards with your service and not forward which all companies should strive for! This is not on...I cannot see that my son has gone from 1GB usage to 3GB...surely if there was a limit of 1GB I would have had the problem long time ago. This should not be left as is and should be dealt with by Cell C. The reason for my review is so that Cell C can see that I might be a drop in the ocean but I still matter...and R15 to Cell C might be nothing but to us hard working individuals that is a loaf of bread that means a lot to us!