Activation lock// seller not replying// stuck😩

hi

just brought a new phone, which I received yesterday from a seller on eBay. Chuffed to get the phone I went to set it up only to be stopped by ‘activation lock’, I’ve tried contacting the seller, but haven’t had any response. Is there any way to bypass this as I’ve just spent $400 on a new phone for myself. Thank you for any help