Complaint , Poor customer service

I was making online purchase on MRPonline using a voucher , My total was R400 and the voucher I was using was R300 , I used the voucher number and reference and it went through, therefore i tried to settle the remaining R100 using bank debit card , there was a technical error and the transaction was unsuccessful. When I re-do the transaction it gives me the error message to say I cannot use the gift voucher , it is added to Mr Price apparel bag , so i contacted them , i have been taken from pillar to post without any help, I have spoken to more than 5 consultants , they all failed to assist me and i want to conclude my purchase. The calls I have made so far are more than the amount of the voucher. I am inconvenience because some of my items are sold out in my bag and the last lady i have spoken to on friday told me the turnaround time to resolve my query is 24 hours, this morning she send me an e-mail to say my query is resolved i can check out but when i check out it still gives me the same error message.It is over 48 hours struggling with the same query