Your servicing lender should be able to provide you with your mortgage account information.
Section 6 of the Real Estate Settlement and Procedures Act (RESPA) provides that borrowers may make a 'qualified written request' to the lender concerning the servicing of their loan account.
The request should not be included with the monthly mortgage payment.
The lender must acknowledge the request within 20 business days and must resolve any issues and/or complaints within 60 business days by correcting the account or giving a statement of the reasons for its position.
A sample letter format is available at https://www.consumerfinance.gov/ask-cfpb/how-do-i-dispute-an-error-request-information-about-my-mortgage-en-1855/
If you do not get a satisfactory answer from the lender, you may wish to file a complaint with the Consumer Financial Protection Bureau (CFPB). You should continue to make your mortgage payment during this time.
The Real Estate Settlement Procedures Act (RESPA) is administered and enforced by the CFPB. If you are a consumer with a question or complaint related to your mortgage or mortgage servicer, please contact the CFPB’s Consumer Response team at 855-411-2372 (855-729-2372 TTY/TDD) 8am-8pm EST.
For more information go to the Consumer Financial Protection Bureau website at https://www.consumerfinance.gov/