The manager doesn't know customer service

We went to exchange a shoe that was bought by somebody else,we realized at the till that we forgot the slip. They tried to trace the purchase but couldn't get the proof of purchase because I was also not sure about the details. So I went back to ask if they will be opening on the 25th..the answer I got was appauling the manager was sarcastic and ubelievably rude. I quote her exact words \ we'll be spending time with our families like you