There are two reasons for your CIBIL score to lower down. First, it may be due to the bank reporting your financial history or personal information incorrectly to the CIBIL. Secondly, if you sign as a guarantor for a loan, but fail to repay the loan even though the payment of EMIs was duty of the primary applicant. These activities can affect your credit score, lowering it.
When you go through your CIBIL report, make sure all the listed details about loan you have taken are accurate. If someone steals your identity and takes loan under your credentials, then report this fraud to CIBIL. Filling an online dispute form is the first step towards rectifying your CIBIL score. And you can find the form on the official CIBIL website.
The settlement of disputes takes about a month, but the process can wrap up much faster if your bank takes limited time in the verification process and other things related to the dispute. Once all your information has been delivered to them from your concerned bank or the lender, CIBIL usually takes only about 7-10 days to update your credit score.
When all the major processes are done, you will be updated time to time regarding the status of your dispute. And if you seem unsatisfied with the manner in which the whole dispute-solving process was conducted, you can file another complaint regarding the issue and the company will again substantiate your personal details and information with the concerned bank.