Product: Checking or savings account

I wrote a check on XX/XX/XXXX from my XXXX account for {$150.00} and put it in a blue government mailbox. On XX/XX/XXXX, {$15000.00} was deducted from my account to pay this check. I discovered this in early XXXX when reconciling my checking account. I called XXXX Bank. They explained to me that my check was most likely stolen from the mailbox and " washed '' to change the amount. I told them that I had a carbon of the original check, the date, signature and memo lines were the same and in my handwriting while the payee and the amount had been changed and were not in my handwriting. I was advised to reach out to the post office to report this and to not report it to the local police as they would say it was a Post Office responsibility to investigate. I was also told that I would be reimbursed for the amount in 6 to 8 weeks. I reached out to the Post Office by phone. I was told that someone would get back to me, but no one ever did. The bank sent me a form to fill out for the investigation and requested the carbon copy of the check. I filled it out and sent the carbon copy of the check to the bank. On XX/XX/XXXX I received a letter from the bank saying that they had received my claim and giving me a claim number. When more than 8 weeks had passed I called the number on the letter from XXXX. I was told that the check had been presented to Santander Bank and deposited into an account at that bank. I was also told that the report said that Santander noted at the time that the check looked suspicious and that the payee and amount lines did not appear to be the same handwriting as the signature and date, and memo lines. I was told that Santander denied my claim ( despite the note that the check appeared to have been altered ) and that XXXX was still pursuing it. I asked if there was any indication of why it had been denied and if there was anything that I could do to facilitate the process. I was told to wait. Since then, I have called back multiple times. I have to start over each time with a new person. I get different stories and different information each time. In late XXXX I was told that it was taking longer because the amount was so high that they had to be sure. Some people have assured me that I will get my money back, others have said that they are not sure, that I just need to be patient. No one can tell me how long this process will take. The call I made on Tuesday, XX/XX/XXXX, took XXXX2 minutes. I finally spoke with a manager that coincidentally was the one I spoke with on the first call. He said he remembered me. He said that Santander was supposed to report back to XXXX about this matter on XX/XX/XXXX and said I should call back on XX/XX/XXXX and ask for him directly. I did that this morning. He was not there. The person that " helped '' me did some research and said that there were no updates to my account yesterday and that she could not answer any of my questions about how long this would take to resolve. After that call, I called the Massachusetts Division of Banks. They said that the banks are regulated at the Federal level and suggested that I contact you and file a report against both banks. They also said that I should file a report with the local police department, which I plan to do today.