DIS SATISFIED CUSTOMER

I bought a 100Gigs voucher for R100 (on special) on friday 02/10/15 and the person who emailed the voucher decided to send me 3 vouchers with no instructions that I should not use all 3. So I loaded the vouchers because I thought it was a series of vouchers adding up to 100Gigs hence I dont know how Cell C works...5days later they call me telling me I should pay R200 or they will reverse all 3 vouchers including the one I paid for!! So basically I'm paying for their *********** sfaff's mistakes! I have proof of 3 emails sent to me without any warnings that I should not use all vouchers..... SO UNHAPPY !!!!!!