Vitality Rewards and Cotton On - System issues or ***** ?

Used Discovery Miles for a Cotton On Reward in mid May 2020 tried to use the reward in mid June 2020. Was told that it had already been redeemed at the beginning of March 2020. This is a date before the miles were used. Have been told an investigation will take 4 weeks. Totally unacceptable as the issue is clearly not mine but Discovery and Cotton On yet I must wait until the two parties sort their problems out. Just credit the Discovery Miles back and I will be happy.