Poor service

My husband and I were at this branch sorting out a return. We then went to the till points to check if we can use a gift card given to us (as we tried a few days before and were told it doesn't swipe and WE must call head office and sort it out but unfortunately we did not get this lady's name) so the cashier (Nonhlanhla mthembu) tries to swipe it a few times & it doesn't work so she calls the supervisor & my husband explains that this is the second time we there with the card to query it & this lady says to the supervisor in Zulu that he is lying. I don't think that is appropriate and down right rude... She was not even apologetic about it. I think this should be addressed as we won't accept this kind of disrespect from staff.