Same Amount Billed for two months

I have a contract in my Dad's name that I pay for and I am the contact person, on the 31st of January 2015 I received a bill with an amount that needed to be paid for R 1083.00, the invoice came with all the breakdowns of my usage and how it arrived at that amount, I happily paid it. Then my February bill came, for the period (01 Feb-28 Feb 2015). AND THE AMOUNT WAS EXACTLY THE SAME they showed me the charged of 'my usage' but the rest of statement was not available because there was no usage for that nonth. and that was because I didn't use the contact sim card for the whole month of February, so how could I have been billed the exact same amount.??? I'm highly displeased by the way Cellc work