Worst online experience and aftercare service

Worst online shopping experience and aftercare service. I wanted to exchange a shoe for a bigger size on the 28th December 2020. I was told to pay an additional courier fee of which I did. To date the shoe has not been collected. I have sent several emails and made numerous calls. No one is able to assist. I have spent more money on airtime to call Crocs than what I paid for the shoe which is absolutely ridiculous. I have never experienced such poor online experience before.