Could i take my car back?

Hi i sold my car bout 8 months ago to my neighbor and told them to change the name of the title to theirs asap. I moved cities and recently i got a call and they told me if i could go and sign a paper so they can renew the registration sticker. This tells me the car is still under my name after so long, so i am planning to get another copy of the title so their copy is null and i can take it back. Is this legal?