Shree Shyam Tele world - Unauthorized bill given by shopkeeper

I have purchased one plus *t *gb ram model from Shree Shyam Tele world on ** may **** with billing amount of ***** ruppes. after around one and half month I want to sale the phone so I put an add on OLX to sell my phone than somebody I got reply from olx told me that oneplus will not give you any warranty on this bill and the same I have confirmed from oneplus by sending an email to them with the bill given by the shopkeeper attached to the maid and I got a reply that the smartphone is purchased from unauthorized store hence OnePlus will not give you any warranty for this phone.after that I contacted the shopkeeper for the original bill of the phone but he is just passing time for almost one month and then he gave me a Amazon bill dated ** may **** which is also edited one.as the smartphone is purchased from Amazon by someone and he resold this phone to me giving me unauthorized bill and now he is not taking the phone back.