Stanley Thermos Not Keeping Warm

I bought a Stanley thermos, but it didn't live up to its promise of keeping my drinks warm. My attempt to return it was rejected because they claimed the product had been used. How was I supposed to determine its ability to retain heat without testing it? I was referred to Polar Star company for an exchange. It's been a month and I'm still waiting for the replacement product, even though I was approved for the exchange after a thorough month-long inspection.