Fill up the form, mentioning that only your phone number needs to be updated. The form looks like this:
3. Submit it at the Aadhaar centre along with an identity proof. Here's a list of the valid documents which are accepted.
4. After submission, your bio-metric details would be verified.
It would take atleast 10 days for the phone number to be updated.
Steps to change mobile number online
In case you want to change the phone number, you could do it online. This method can be used if you don't use the mobile number used registering with Aadhaar. However, your already registered phone number linked to Aadhaar need to be functional for generating the OTP.
Click on the Aadhaar self-service portal under the Update Aadhaar section in the UIDAI website. It looks like this:
2. Enter the Aadhaar number and the verification captcha text to generate an OTP in your existing number.
3. After submitting the OTP, a new page appears for the updating the new details.
4. Select 'Mobile Number' under 'Select field(s) to update' and enter the new mobile number.