They refused to accept my Absa challenge voucher

I went to Steers at Mabopane Square an I wanted to use my Absa challenge voucher to buy and the cashier by the name Elizabeth Rampotla refused to take my voucher number she said they are not allowed to use vouchers anymore because the vouchers always bounced when they cash up at the end of the day so they are not allowed to take them, she did not even ask what type of voucher am I going to use she just refused and she said she can even call the manager, the manager will tell me the same thing. I'm surprised because I always use my vouchers at Steers and I never came across a problem and no one refused to take my voucher, I'm not happy at all about service I received regarding that.