Ordered Pre-Owned Phone and it was defective; next steps?

Dear Boost, can you please assist with this:

I ordered a pre-owned Samsung S6. It arrived yesterday and when I turned it on, I noticed the Home button was not working (touchscreen/volume/power buttons worked). 

I want to get a refund but I'm told that I need to pay to ship it back... I understand if I don't like it, I should pay to ship it back; but the phone was sent to me defective, can you please provide a prepaid return label or provide me an alternative solution where I am not out of money for something that should have worked in the first place (like return to Boost Mobile store).

Thank you.