VPower reward card

Thr V Power reward card I have in my possession is of no use to me. I've gone there twice and tried using my card, but my pin is rejected by the system. Today I was told to call the number on my card. I'm a pensioner and don't have money to be calling them. I emailed them but never got any response. I'm not impressed. She'll South Africa is free to call me any time at *** or email me at ***