prepaid electricity

I bought prepaid electricity on Saturday 4 Nov 2017 at Pick n Pay in the Menlyn shopping centre, got home just to find out that I cannot read in the voucher as it gives me an error code - used. Tried to call them but no one answers the phone. Drove there on Sunday and spoke to Ass Manager Ayanda who took my details and undertook to find out what the problem is. No one contacted me on Monday and I once again tried to call the Menlyn branch nomerous time and nobody answers. Drove to City of Thswane and they pointed out that the voucher given to me by Pick n Pay menlyn was already used on 26/7/2016. Drove to Pick n Pay Menlyn again after trying to call, showed Ayanda the Tshwane printout and waited about an half an hour and that was when she told us that she would phone me on Monday with a new voucher number. Nobody called on Monday and I then tried to call their customer help line but after holding on for another half an hour was told that they would get back to me. Once again nobody called so I tried to call Menlyn branch with nobody answering then called the customer help line again, spoke to Phume who realy tried to assist but was also unable to get hold ofanyone at Menlyn branch. Phume took my details as she arranged withh the pick n pay clothing in Menlyn to et the manager of the Pick n Pay to call her or to get the manager's cell phone so that this can be sorted. This is really unacceptable