Standard Bank not reversing moneys paid into wrong account

I have started a company (Pty) Ltd about 2 years ago and opened a bank account with Standard Bank, which Standard Bank gladly opened for me, the problem is that my Dad also had a account with Standard Bank, which I used a very similar name as to my Dads business name, but also he was a cc and I am a (Pty) Ltd which totally a different entity as to my Dads business. My Dads company had a lot of problems and he was forced to close his business down, which he is not trading anymore and because of all the stress he decided to leave me and go and look for a job elsewhere. I then decided because I worked in his business that I could do the same as what he was doing and went to customers which excepted me very well in the market place and also went to suppliers and got my business going, the problem that I have with Standard Bank, that a lot of these customers which I supply to has been making payments back to my Dads previous business account and I have been losing money and I cannot pay my supplier. I have tried to force the customers to get the money back from Standard Bank, which the response from the bank is there is not sufficient funds, which I understand because as far as I am aware of, he had an overdraft facility with Standard Bank, I feel Standard Bank cannot hold me liable for my Dads accounts although I have a similar company name cannot take over his debt with Standard Bank, my business has lost up to R+-R 75000.00 because of all of this, and I don't now how this matter can be resolved