If you bought the phone online from a company, you should have at least 14 days to cancel your order. This gives you the right to return the phone without giving any reason.
Another possibility is: explain the situation to your supplier and ask him to exchange the phone.
Another option is to wait for /e/ OS 9-Pie and hope that an OS change is possible. (Note: this isn’t meant cynically!)
Only you can decide which is the right procedure. Think positively.