Ariana Grande and Tekashi 6ix9ine are having a wild back and forth via Instagram after her charity single with Justin Bieber “Stuck with U” debuted at number one on the Billboard Hot 100 ahead of his new post-prison smash “Gooba.” After Tekashi, 24, railed about how Ari’s single had an alleged final hour sales boost, he accused Billboard of manipulating the numbers in favor of the two singing superstars. Ari, 27, clapped back and even Justin, 26, ended up weighting in to the feud.