Lack of response regarding online returns

Order trainers online on black friday - once they were delivered, realised they were big. Followed their procedure for a return (as they apparently do not do exchanges!!! Took a few days before someone responded to say they will process the refund and get the courier to come pick up the trainers from me. 3 weeks and still nothing - no communication - useless online customer service people who respond with standard/generic responses! Im told the courier SHOULD HAVE come already (No communication to me as to when so i can ensure someone is available to hand over the goods) 5 days ago i was told it was escalated - still no communication. Absolutely shocking, appalling service from such a big global brand! All i want is to either exchange the shoe for the correct size - or give me a refund and come collect the goods!!! But zero communication is not acceptable!!!