Product: Credit card or prepaid card

I am detailing the occurrence between Chase Credit Card and myself, with dates that I documented and to the best of my ability. 
The issue listed plainly is as follows ; my sons XXXX XXXX was stolen from his dorm at XXXX XXXX  ( we believed by his roommate ) We never followed an official police report, only the campus police was told and they did what they could, however, since my son and his roommate would both still be at the school we did not want any further issues. My son was given his own room away from the original building he was staying in. My only concern was the credit card, which I had for over 10 years. I have 4 credit cards from Chase, I have never been late nor had I ever not paid the bill in full  every month. 
I called Chase to let them know that the credit card number might be in the stolen XXXX XXXX, but I was not sure, they stated that I could lock my account to give me time to either find the XXXX or to find out for sure if the card number was on the XXXX XXXX. The lady told me that she could not do it, I had to do it myself, and walk me through the process as I was on their website and followed her directions. 
The following month I received a bill for $ XXXX all from the XXXX XXXX, I called and told them how can that be. They stated that once you locked the account no purchases can be made with that card. Even their commercial on TV said it. They cancelled my credit card, issued me a new one and I started the process of filing a fraud report. 
The fraud department concluded that since I had received a benefit. I would have to pay. They can still not tell me this benefit I received. 
Depending on whom I spoke with in the fraud department, their reasons changed as to why I had to pay : I had used this merchant before, and they allowed the charged to go through as a courtesy to me. 
I had paid already one of the days in the previous bill that was within the block dates ; therefore, I must be lying. I was going into XXXX and I did not check the bill carefully, all I wanted to do was to pay the bill and lock my account. 
I need a police report to show that the XXXX  XXXX was stolen. ( I was not asking for them to pay for the XXXX XXXX ) I followed their instructions to safeguard my account and credit card and their system is flawed. 
Not once has Chase taking responsibility for the occurrence. My theory is that if they admit that they system does not work, ( lock your account and no charges can be made ) they might be heading for a class action law suit. I can not believe that I am the only one that is going through this. 
Since the occurrence my credit score has dropped from XXXX to XXXX. They also stated that I should of known that even though I am still fighting the charges I needed to pay the bill first. No one has ever told me that other than one of the supervisors at their executive offices named XXXX after the damage to my credit was done. Please note that I will NOT pay that bill, it is wrong, I did not receive any benefits and they are lying. 
On pervious bills my son used the card for groceries, gas, and entertainment. The bill is question only had XXXX XXXX charges. Chase has to be stopped from this abusive behavior, which has no basis. 
Thank you for your assistance in this matter which has taken a toll on my health.