How long for fraud to be resolved

Found out today that someone hacked attached my personal tax account and managed to get 24,000 paid into their account in sept last year leaving me now with a liability over 17,000 and climbing. First I heard was a letter re liabilities last night. They used different name and address to me for the bank account plus I have paid in via same bank details last 23 years - I am beyond furious and spent 5 hours trying to find out what has happened after first self assessment agent said there was no fraud! Then second agent revealed this 24,000 transfer last year. The second agent says they have sent email to fraud department. I can't make any payments in case they get in and take again. Can I find out when I will be contacted about this if there is any specific telephone number ( I have reported to action fraud on agents advice) and of course if this has happened I cannot be liable for any accruing interest ?

Hi

I am sorry there is not a specific number to contact.
The referral has been sent to our fraud department. We do not have a timescale for when you will be contacted.
When you reported the details to action fraud they would have notified you of their procedures. 

Thank you