Why is Woolworths with a new app taking customers cash back away

Terrible ,Pathetic service for the past three months ,I had no joy trying to sort out my Cashback that was taken away .I have been a black card customer for the past 10years ,but since they changed their app ,they cancelled my more than R5000 in cash back .Is this the way Woollies want to increase their profits by *****ing form customers ,if it was done to me ,how many thousands other customers money was ****** in this way ,absolutely unacceptable to be treated in such a way and to be given the runaround for three months.