The worst service

I bought black pebbles a month ago on the 26th of February, with a 10 working day delivery promise. To date I am yet to receive my purchased order. I cancelled the order and asked for a refund on the the 19th of March as delivery did not happen even after I have given them a grace period. The purpose of buying the pebbles has passed and is of no use now because of the timing. Since then I have not received no correspondence from the company. Please advice on my refund. Thank you