No one can assist with car paper

Struggeling to get my Mazda car papers that i've paid for for a few years now, it's up and down and up and down. I've paid the fee and still nothing, i've called the call center who asked me to mail the POP, i've dont that and still nothing, today i called, i dont exist on their system. Who can please help me to get my car papers mailed to me. Ive sold the car and need to hand it over to the new owner.