Who is making money here

We hired a vehicle from Hertz on the 24th Sept and a hold was put on for the deposit. On the 13th when we followed up with Hertz we were told that release of hold had been sent to FNB on the afternoon of the 13/10 at 15:30, and should be release in 24 hours. On 15/10 we followed up with bank and Hertz. Hertz provided us with a email showing release of hold sent through. FNB told us would be handled soon. We are now 8 days down and still waiting on the hold to be released? So is FNB holding onto a payment so they can generate interest? Or while they reimburse us with interest.