Banana Republic Freadulent Offer San Francisco CA

I received a $10 Banana Republic mobile gift card over the weekend that was supposed to be valid until May 30 which could be used with their 40% off Hello Summer promotion .  Today, I drove to the mall after work and tried to use my mobile gift card,  but Banana Republic had blanked out my code.  I texted them for help and received an automated reply that they had ended the promotion early and had cancelled my gift card without any notice.  I called Banana Republic customer service to complain as I had driven all the way over to the mall after a long day at work and was not happy.  After waiting 30 minutes, I was connected with representative B. who seemed shocked at my plight and that I had not contacted the store manager who would have okayed my credit.  I told her I was still at the mall and she said she would contact the store manager about the situation.  I waited another 10 minutes while this was done, she said the store manager was aware of my situation and would find a way to make things right.  I went into the store to make my purchase and was told by the manager K. that she would not honor my mobile gift card and that that was completely opposite of the conversation she had just had with B.  In addition, even if they did give me a credit, Banana Republic had changed the rules that morning and would not allow it to apply to anything on sale.  She called B. to complain and this time (unlike me who had to wait 30 minutes) was able to instantly connect with her and this time B. changed her story and said she did not say the manager would honor the $10 discount.  I have never encountered such "shady" business practices and disrespect for a customer before.