My client had the exact same issue as you. She was admitted to the United States on a B2 Visa from June 18, 2014 until December 17, 2014. We timely filed an I-539 on December 15, 2014, requesting an extension of the tourist visa until June 15, 2015. As of June 2015, no decision was made on the I-539. On June 15, 2015, I timely filed a second I-539 with a copy of the receipt for the first I-539. On November 17, 2015 I received two approval notices in the mail, one for the first I-539 and one for the second I-539. Therefore, you should timely submit a second I-539 with a copy of the receipt for the first I-539.