Bad service from Manager

Terrible customer service from Michael at Plumstead prospur Clicks. I buy online so had tho huggies nappies size 5, opened one and realised they are small. Went to exchange with my delivery note and he refused to exchange them without the invoice in case the price changed and there is need to pay the difference. What nonsense is that.? He was rude, dismissive and loud. I didn't expect such service from Clicks. I have been a loyal customer for years. Couldn't exchange the nappies cause I have no invoice but I have the delivery note! And that kind of attitude to the customer as a manager No!! I live a minute away from the store, I would have gone home to get my phone, but his tone and attitude was disgusting. I guess it's goodbye. Managers need customer orientation on the mind regardless