I understand. Sometimes this sort of thing can lead to criminal charges. A common scam is to go to a bank machine, punch in that you're depositing a cheque or cash, insert an empty deposit envelope, then withdraw the cash right away. That's fraud because you're lying to the bank about having deposited money which you then want to instantly withdraw.
That's not what you did here, you asked the bank to move funds from one account to the other. And the bank did that. So there's no fraud. If the funds weren't available or you didn't have sufficient overdraft, then the bank should simply have declined to complete your transaction.
Clearly you overdrew by accident. This sort of thing happens, and I'd be very surprised if the bank tried to have you criminally charged. As you've observed, you're paying the money back and you ought to be more careful about telling the bank's website to move around funds that haven't yet landed in your account or cleared, but it's as much the bank's fault for allowing this to happen as it is yours, from what I can see.
When you're seeing the bank manager on on Tuesday, ask flat out why the bank allowed you to transfer funds between your accounts if the funds weren't technically available in the first place, and that you're going to replace the funds that you inadvertantly borrowed from the bank, and ask about overdraft options to prevent this from happening in the future. There's no reason to act guilty or scared.
The bank will likely say that they froze the accounts automatically because of the potential for fraudulent transfer, or because these circumstances sometimes indicate unauthorized access to your accounts.
Does that make sense? Please reply with question or comment. If I've answered you then I'd appreciate a positive service rating please.