Product: Debt collection

In XXXX, I signed up for a security system with XXXX ( See Attached contract ). They later became XXXX. In XX/XX/XXXX, I left the house in in question and moved to Virginia. In XX/XX/XXXX, my divorce to my ex-spouse became finalized. According to the Property Settlement Agreement ( See Attached Paragraph 1.4 ), we separated our property in XX/XX/XXXX. In XX/XX/XXXX, I changed all the bills associated with the home into my ex-spouses name including the home security system. Also, Paragraph 5.4 states Wife is awarded the home in its entirety to include the present the present and any future equity. Wife shall be responsible for paying the mortgage and other living expenses associated with the home. 
In XX/XX/XXXX, a Collection Company, Hillcrest Davidson contacted me about a debt they were trying to collect on behalf of XXXX. I went through the explanation of the divorce and explained that the debts associated with the house ( including the security system ) were the responsibility of my ex-spouse. They told me they had a contract with my name on it. I asked for it and they said I needed to send them an email to request it. I sent them the email and in response, they sent me an email stating that I was not responsible for the debt. 
I did not hear back from them again until XXXX XXXX ( XX/XX/XXXX ). They left me a voicemail. I called them back and the representative that called me wasnt available. They told me it was about the debt for XXXX. I again told them about the divorce and that I was called by them or a different collection company about this same debt and that I was not responsible for it. The person on the other end of the phone said he had to talk to his manager and would get back with me. 
The next day, I was called by the representative that left me a voicemail. I again went through the story of the divorce and that this bill was not my responsibility. I explained that the divorce decree ( court order ) gave the house and the bills associated with it to my ex-spouse. She said I had signed a contract. I then went through the story of the prior call in XXXX of XXXX. She said that it wasnt them that called, that this was a new account. I again asked for a copy of the contract. She gave me their email and said I had to request it. I took their email and said I would request the contract. After we ended the call, I went back and checked my old emails for the XX/XX/XXXX email stating that I was not responsible for the debt. I found it and saw it was from Hillcrest Davidson, the collection company ( See Attached ). I called them back and read the XX/XX/XXXX email back to the representative that called me. I gave her the account number that was on that letter. She sent me the contract and said that she had to speak with her supervisor. She put me on hold. Her supervisor came on the call and said that I had signed a contract so I was responsible. I looked at the contract and saw that it was my signature on the contract from back in XXXX. That it was a 3-year contract and should have ended in XXXX. He said that the contract said it would re-up yearly after that. I explained the divorce story again and said that the decree gave the home and the bills to my ex-spouse and that I transferred that over to her back in XX/XX/XXXX. He said that the contract required a letter from XXXX stating that. I said that I contacted the company that billed me XXXX XXXX XXXX, took my name off the account and gave responsibility to my ex-spouse. Our conversation got heated and he said that he was going to send the bill to collections that day because I was refusing to pay. He hung up on me. 
I called XXXX that day to dispute the collection account. Later that night, I called XXXXXXXX to dispute it there and they didnt show any record of the collection clam. I called CFPB the next day after the collection company called me again just to hang up after I again went through the divorce explanation. 
I am not responsible for the debt. I believe they do not want to go after my ex-spouse for collection and are attempting to get payment from me. They initially went after her ( as indicated by the letter ) and must be trying to get something from me because they were unsuccessful going after her. They didnt want to hear that the bill was my ex-spouses responsibility and sent a 60-day late collection notification account/alert to XXXX after talking to me twice since XX/XX/XXXX. They irresponsibly tarnished my credit score after talking to me for two days about a debt that isnt my responsibility. My XXXX  score dropped over 100 points! Please investigate Hillcrest Davidsons over-aggressive behavior and have them restore my credit score by removing the erroneous collection that belongs to my ex-spouse.