FNB bad customer service

Hi. On the 09th of December 2017 I bought electricity for R350 on cellphone baking. The voucher number that I was sent was an old voucher number. It kept on saying its been used, when I tried to put it on my meter. I then called Tshwane municipality and they said I should come to the office. We went there and they confirmed that the voucher number that I was sent was used I. 2016. They said they can't help me I should call cell phone baking department. I went to my bank explained the matter and the bank manager told me unfortunately they can't assist me, they gave me a phone to call cell phone banking department. I then made a quiry and they said they'll investigate the matter, which will take 7 days and indeed I waited for 7 days. After 7days they sent me exactly the same voucher number with had been used. I called them again. Now it's been seven months, I'm not getting any help and my money was deducted from my account. Please assist.

Thank you