Bank Transfer gone wrong

[Jeebz92]

So I made a bank transfer last night from my Natwest account to my Halifax account for £2000 - Normally, such payments are there instantly however it's been 24 hours and there's nothing in my Halifax and the money has been deducted from my Natwest account.

I've triple checked all the details and they are all matching and correct - Yet for some reason my Halifax account has not received the payment? They say that it takes a max of 24 hours but it's now been a day and nada.

I spoke to Halifax who said they can't do anything because Natwest sent the money. Natwest say they've sent the money already and don't have it.

????

What is going on here? What can I do?