Unhelpful Takelot

Recently bought Accu Answer Cholesterol test strips . Cost R600 for 25 . Only 8 worked . Sent back to Takelot but the return was rejected by one Kennedy as they were used . HOW ELSE CAN I DETERMINE THAT THEY WERE DUD ? no response from him or customer services when I asked for suppliers details ( D & A HEALTH) so as to deal directly . I am not new to testing and the other strips worked fine .