Please return my items

Recipient did not receive delivery however Fastway are insisting that delivery was made. I have requested proof of delivery from Fastway on a number of occasions but they are non-responsive. The phone number provided for queries is always engaged. I paid to get something delivered which was not delivered and I cannot get hold of them to return the items. I no longer care about the items being delivered and I just want them returned to me. Can anyone help me to get hold of them to return my items. They can keep the money I paid for courier as I am past that point. I just want my items returned.