Standard Bank

I have been fighting now for almost two months for Standard Bank lift an authorisation on my account. Initially they said they don’t have the email to lift hold on my account. Then one of their agents sees that an email was actually sent but Standard bank still had not lifted the hold. She resends the email and asks that I give them 24hrs. Three days later the matter was not resolved. I then asked Avis to send me these emails so that I can send them directly to the cancellation department but alas Standard response by saying I am not allowed to send this myself. But when Avis sends the emails they claim not to receive them. What must I do now? This is my money they are holding for no reason.