Very disgusted with Adidas

I ordered a jacket and it was too big so I logged a return and the courier came to collect it… I waited for my refund until I realised it was not going to happen . When I reached out to adidas they keep on telling me stories which insinuates that they had problems between the courier they entrusted to do the job and then BUT I am the one to suffer as they won’t pay me back my money because they can’t trace what happened after the courier collected the order. I’ve tried to let it go because I was just tired of fighting but every time I think about my hard earned cash I become so angry that such a big brand can **** people just like that 😡😡😡