Missing airtime

I paid for my mother's cellphone - *** and since her upgrade her airtime is depleted in the first week - she never download anything thing or access on site that require internet access. She only uses the phone for Whatsapp and to make calls but she has not even made one call as she never has any airtime<br> <br> She has wifi at home which her phone is connected to.<br> <br> I tried to phone 111 but the voice prompts only wants you to do a voice password which I do not want to do, I would like to inquire as to where her airtime goes. I loaded R100's airtime this past Sunday, 11 October 2015 and already yesterday she had no airtime she has not once made a call or used the phone other than it being connected to the wifi. My brother - *** is on exactly the same package and he never runs out of airtime.<br> <br> My concern it that she will not be able to contact me in case of an emergency due to no airtime, which she has not even used.<br> <br> Please can someone get back to me on ***.