If it was broken when it arrived, and you received it less than 30 days ago, you can start a return using the Ebay Money Back Guarantee.
For future purposes, check the seller's feedback and, for the sort of purchase you made here, check that the seller is a properly registered business seller with a legal returns policy.
A private seller is just selling their own, generally secondhand items and does not have to accept returns. Private sellers would not have hundreds of phone holders for sale.
"There are two ways to be fooled. One is to believe what isn't true; the other is to refuse to believe what is true.”
Søren Kierkegaard, Danish philosopher (1813 - 1855)
