Still no feedback regarding WhatsApp query

a few weeks ago I noticed that I am being charged for whatsapp from my airtime this never happened previously I recently had an upgrade on my contract I have a Z3 now I called in & I asked about this I was told that I am not suppose to be charged for the use of whatsapp I have not airtime left I am still waiting for cellc to get back to me regarding this matter I called on the 29th of April & again yesterday the 05th of May but still not assistance regarding my matter, you advertise something that is not even true than you have the audacity to charge me from my airtime I need this matter resolved today