Rude manager

The manager at mugg and bean was rude and had an attitude towards me! Since it was my birthday on the 18th of June I went there to redeem my free cake slice that I had been rewarded on the app. A staff member was kindly helping me with redeeming when the manager came and shouted at her and made an excuse about loadshedding and that being the reason we can’t redeem but that didn’t make any sense so we tried to tell her to explain to her further but she was just dismissive and rude and told us to leave as there will be no cake we will be getting ! I’ve never been so appalled by someone’s behaviour before! The mugg and bean I went to was at suncoast Durban