Food voucher competition

I was in August about competition that took place at Econo food silverton in May for R1000 food voucher which i was told to collect before 30 days , i went to the store on the 16th september an was given a very cold treatment which i was told my name was not there an i should leave copy of my ID, an contact details, i did as requested an i never recieved any call from the store, i took it upon me to call headoffice an the lady confirmed she called me an will make follow up, i have been calling an im told there head-office must respond, im not happy with how this matter is being handled as im not getting any assistance an no voucher since last month , always wen i call im told they will fix but nothing is being done