LaVar Ball's JBA league is now facing allegations from a former player that he got stiffed out of his full paycheck ... but, just last week, LaVar was adamant he's paying ALL of his guys. 

Brandon Phillips -- who played for the L.A. Ballers this season -- claims he's only been paid roughly one-third of what he was promised ... and had to come out of pocket to pay for travel expenses.

Phillips told Cycle Media's Thomas Duffy that no one from the league has returned his calls regarding the 2 paychecks he never received.