Cell C the lowest rates on data that you don't get

Hi i have a data contract with Cell C the contract has lapsed and i am going on with a month to month basis, i have many contract with cell c, i notice in the past few months my data is being depleted very quickly, this month it was not even 3 days and 5 gigs are gone, just like that, the irony of the matter is that i keep getting calls from cell c to ask me to renew the contract as there might be a price increase etc and hold and behold all my data gets depleted i find that really amazing. when i called cell c they tell me that it is internet usage but to my knowledge my wifi was shut off and two days later i am out of data, i have been given a a reference number and no one can certainly tell me if the usage is legit or not. Cell C says that they have the lowest rate on data that because they do not give us what is due to us, i am sick and tired of being ********** like this