How can I get a free upgrade to business class on Delta Airlines?

???????????????????????????????? ????????????'???????? ???????????????????? ???????? ???????????????????????????? ???????????????? ????????????????, ????????????'???? ???????????????????????????????? ???????? ???????????????? ???????????????????? ???????? ????+1~(833)~730~7587(OTA)????. ???????????????? ???????????????? ???????????????????????? ???????????? ???????????????? ???????????????? ???????????????? ???????????????????????????? ???????????? ???????????????????????? ???????????????? ???????????????? ???????????????????????????? ???????? ???????????????????????????????????????????? ???????????? ???????????????????????? ???????? ???????????????? ????????????????????. https://www.eventzilla.net/e/how-can-i-get-a-free-upgrade-to-business-class-on-delta-airlines-2138651218