Bad customer service

I bought shoes for my daughter late last year as she was going to University this year. Most of the things she took with her were new. When she was away she realized that one of the pair of shoes doesn't fit and she couldn't change them because she didn't have a slip. She came back with the shoes and I to Refinery the glen mall to get the size to be changed but they couldn't assist as they say it's over 3 months even though I still have the slip. They promised to call me back when the supervisor is at work but up to now I haven't received the call. I'm stuck with these shoes