Reebok Shoes — unable to redeem coupon

Address:

Ghaziabad, Uttar Pradesh

my self saurabh shukla . my booking id is [protected]. i am unable to redeem coupan came along with my invoice. i have done all the stage stated behined coupan an error message is displaying on screen that invalid order no or gift has been allocated aready . in both cases i have done nothing wrong neither order no is wrong nor i have claimed for gift before . so please help me regarding to redeem coupan