Wrong Mobile Number Linked to a Bank Account – Need Advice

My friend is receiving transaction messages (ranging from ₹50K to ₹1 lakh) from a bank, even though he doesn’t have an account with them. Based on the messages, it seems that his mobile number is linked to someone else’s savings or current account.

We contacted the bank, provided screenshots, and even visited the branch, but they refused to help. They insisted on providing a passbook or account details, which we obviously don’t have.

We also checked his credit reports from all three major agencies, and there are no unauthorized loans or accounts linked to his name. However, the constant messages are causing concern.

We tried raising a complaint with the banking ombudsman, but it requires an account number, which we don’t have. What should we do next?