Utterly disgusted by the kind of service received from Woolworths Financial Services!!!

I received a quarterly voucher from Woolworths and when I tried to redeem it the voucher scanned invalid. this was tried by scanning and manually sadly it didn't work. I was told by the supervisor to contact the department responsible for it to correct this and was then advised it should work now but to my disappointment it obviously had the same error "Invalid". Again I was told by a supervisor to contact them. I emailed once again only to be told that the voucher was used the first time I produced it. I asked them on what and who used it because I paid for my goods in full, I was told they can't say unfortunately and that I have to go back to the store where it was used. There is a trail of about +- 10-15 emails back and forth but no resolution because we as customers of Woolworths is not worthy enough of getting the necessary assistance we need. I was being made out to be a **** and a ***** by Woolworths and felt utterly disgusted from this experience.