Unhelpful customer care service

Okay so I bought voucher at naiboom total garage yesterday. When I put the pin it's keeps on saying invalid pin, I called Hollywood customer care so many times with no luck of any help. So I don't know what to do...I will just feel like I've wasted my money and cos I've been trying to put enter the pin so uncountles time even tried on some other things accounts but nothing is happening.