Answered on March 23,2018
You have to visit nearest Aadhar update centre to do it. It will cost you INR 25.
Answered on January 30,2019
Mobile number update in Aadhaar requires Biometric Authentication, it cannot be done online. Please visit your nearest Aadhaar Kendra (Locate one from: https://uidai.gov.in/ ) for this. No documents required for mobile update.
From January 2019, it will cost you INR 50 to update it.
Answered on December 03,2019
You can check this video to update Mobile Number in Aadhaar card.