Unallocated R500 voucher

I am utterly disappointed i the dealings with Vodacom as a marketing lady called for a survey and advise on their current brand positioning. i was promised a R500 voucher and the call was for an hour and a couple of minutes. I was sent a Standard Bank voucher that has no pin tried contacting the lady but could not reach her. i would like to redeem my voucher pin so that i may access the funds that are due to me.