Very stressed!!!

Im very stressed right now because i bought a pre paid electricity voucher using fnb bank and fnb does state that should anything happen with the voucher it wont be liable, so now the buck stops with Erkhurhuleni municipality. i have called the call centre and the gave me phone numbers to call ***/ 5657/ 3831 being calling since monday and theres no answer, so now im not sure if i should go to their offices and they will be able to assist me if nobody cares to answer their line. i cant just let R500 down the drain. the voucher doesnt want to load.