IDFC Bank — Regarding faulty linking of phone number to someone else's loan account

My mom is sick and under treatment. This bank has linked my moms phone number to someone elses phone number without verifying the kyc. My mom is constantly getting abusive calls from the loan collection agents and text reminders insisting her to pay someones loan.This has been happening for over a year causing mental stress and pressure ony sick parents.After reaching customer care multiple times the bank assured in email that my moms phone number has been removed from their kyc records. However my mom is still getting abusive calls and loan repayment reminders disrupting her normal life.