data just disappears and no answers

I bought 1GB of all network data for my mobile number on the 18th of August 2015. to my suprise i recieve an sms saying that i am left with 500MB i check if all my apps are off as i am doing that another sms's comes in saying i have 99mb left in a space of 9mins. I than try calling the call center and no one picks up around 9am today when the incident took place when i was giving up another smses pops up saying my data is used up!!!!! finaly at around 2pm a lady by the name of Asnanda picks up i tell her the nature of my query and she states i can only get assistance from the data management department she than puts me through but still no answer!!!!! i call again and request to speak to a senior but non was available!!!! the lady that was assisting me than said i should go to their nearest store to find out from their IT person what happened. however i see no point in me going there, the only thing i will want to go do there is to find out how can i get out of this contract i have with them!!!! i had so much love for this company as i could count on them but since this incident i am not to sure where their faith in a customer lays. even with the 500mb i recieve it doesnt last long