Disappointing and excuse for customer service

Very very very bad service. I went to builders express craighall to redeem a voucher which I got from one of the builders warehouse. When I walked in I went to the information counter, I ask a lady if I can redeem it, showed her the voucher then she said I can and directed me to the tills. When I got the lady by the name of Keabetswe said, she can not assist because I didn't get the voucher from them and she showed me lots of slips but failed to explain why she couldn't assist me and rather gave me a hostile attitude. It's so unfortunate that we as customers receive such putrid service from people who are suppose to be helping us, maybe someone should teach Keabetswe some manners and work ethics.