Stanley mug not keeping warm

Bought a Stanley mug from this Company a while back,never used it because it did not keep my coffee warm. Took it in,they charged me R100 for shipping to have it checked. Apparently the lid was faulty,when I got it back yesterday 15/10/24 ,I tested the mug at home,still not keeping the coffee hot,not even close,as a matter of fact,I filled it up with hot water together with my 'cheap' Checkers mug,guess what!! The Checkers one was keeping the water at a higher temperature than the Stanley mug,not hot,but warmer than the Stanley. I cannot drive up and down and pay courier costs to have this mug tested all the time. What are you going to do about my predicament, by the way,my name is also Stanley,what a disappointment. My Stanley flask is still working 100%,after been replaced once. Stanley Theart