Contact the Police and the bank.
Many years ago I received a check in the mail from my bank marked "RETURNED - CLOSED ACCOUNT". My bank indicated that they would not honor this check that I "cashed" at my bank and they were billing my account for the face value of the check plus fees. The value of the check was $700.00. I looked at the check, a personal check drawn on the account of a person whom I had never heard of, made out to me, endorsed by me (seemingly), and apparently cashed at my bank with my bank account written on the back of the check. Upon closer examination of the endorsement, the signature was close - but some key elements of my signature were missing (and I NEVER sign without those elements of penmanship - and excuse for not indicating what they are here <g>).
I called directory assistance for the person to whom the account belonged to and spoke to him. He said to contact the Police in his community as he had a box of new checks stolen from his mailbox and had filed a police report, and this was not the first check someone called him about. I contacted the police and talked to the detective in charge and he gave me the case # and told me what to do/say with my bank and to give them his contact information. He then asked me what I thought was a very strang question ... did I apply for a mortgage recently. YES!! I had indeed just applied for my first mortgage (this was back in 85). He then asked who with and I told him, and he said that was the same mortgage company as the other person who this had happened to.
Apparently someone at the mortgage company has my bank account number and my signature on the mortgage documents. They then steal blank checks. They make the checks out to people with recent mortgage papers where they have account/signature - then they go to that person's bank and cash the check as if they were me.
I contacted my bank, and they said that there were two more checks that they had mailed back to me ($850, and $560) both charged to my account, and they had THREE MORE checks that day that they were about to mail back. They asked me to come in and sign an affidavit. When I got there they had already viewed the video of the person that had cashed these checks and were able to verify it was not me.
They refunded the monies back into my account and fortunately I had not YET had any of my own checks returned NSF due to the bogus charges.
I have no idea if the bank ever recovered their money, or if the person was ever caught. I certainly hope so.
It was certainly an ordeal.
I'm really floored though by the fact that it had to be an employee of the mortgage company that was using data to steal. It's not like you can get a mortgage without this data ... so who are you going to trust?