Heat grill to medium-high heat.
Heat oil in medium skillet on medium heat. Add plantains and garlic; cook 4 min. or until golden brown, stirring frequently. Stir in beans; cook and stir 1 min. Remove from heat; stir in onions. Cover to keep warm.
Grill franks 7 to 9 min. or until heated through, turning occasionally and topping with Singles half for the last minute.
Place franks in buns; top with plantain mixture and mayonnaise.