Brian Pumper and Montana Fishburne in a scene from "Phattys Rhymes &Dimes 14"

*Montana Fishburne claims she was cheated out of payment from her sex tape partner and has hired an attorney to help reclaim it.

TMZ has obtained several letters that Fishburne’s legal team sent to Brian Pumper demanding that his production company immediately stop all sales of “Phattys Rhymes & Dimes 14,” which includes a scene featuring the two of them.

According to the letters, Montana never signed a release for Brian to use the X-rated material in his video, the website reports.

Fishburne says she was in the scene in the first place because Brian offered to help her “practice” for her big professional debut with Vivid Entertainment … and the footage wasn’t supposed to be sold.