Capitec stole my money

In 2018/10/15, I transfered money from my fnb account to capitec. After a few days she informed me that she had not received the money. I contacted my bank and they assured me that that the transaction was successful. I had to reimburse the funds because Capitec insisted that the payment did not go through yet I am certain that the amount left my account successfully. I tried calling the bank, however they said they could not assist me since I didn't bank with them. It has been a back and forth up until now I did not get my money bank. R1500 is a lot of money and I want capitec to pay me back.