10 Months to Discover a Mistake!

I am very concerned about the way my account is handled and the security there off. On 24 November 2017 I made an EFT Transfer to my husband's account. On my side and on my statement it shows that the transaction went through once. On the 13th of September 2018, my husband received 3 threatening sms messages from Nedbank regarding the R650.00 that went through twice, that they will PROCEED with LEGAL ACTION at his WORK and HOME because of this. I am the Nedbank account holder. Why does it take Nedbank 10 months to discover the mistake, with no correspondence what so ever? The people at the number given did not want to speak to me, they wanted to speak to him, then they wanted to speak to him again and then to me again. With this going back and forth I lost my temper and told the call centre agent that your system is up to ****. I am really contemplating closing my account because of this mix up.