You are covered by Paypal for 180 days from PAYMENT.
So if you paid in January you have until July to open a Not As Described dispute.
The longer Dispute period is offset by PP's insistence that the buyer pay for return shipping with Confirmation of Delivery.
If your seller is not in Canada , this will run you $40 or more.
You will not win the Dispute if you do not return the phone.
You will not win the Dispute if you do not use tracking (Delivery Confirmation).
PP's Resolution Centre is at the top of the account page under Tools.
Do NOT get into a conversation with the seller.
You want a refund, not a replacement.
Once you prove the phone has been returned to the seller, you will be refunded.