Account complaint

I am receiving accounts that really are way too high on cell phone number ***. End January 2016 it was R839.18. End February 2016 it was R1402.82. end March it was R1909.95. The said cell no is mainly used for calls and whatsapp. I really want to know what is going on on my account especially this number. Why did it double? Client service really does not help, they let you feel like a idiot.<br> I have two data bundles and use my computer for any research to be done and emails. could you pls assist in helping my to try and find out what is going on.