Yes, you can. You can update the account via the FairPrice main website or by using the FairPrice Group app, just follow the following instructions:
FairPrice Website
1) Click the "Account" button at the top right of the website
2) Select "Edit email" under Profile
3) Edit your email address
FairPrice Group App
1) Click the account button at the top left corner of your screen beside the LinkPoint logo
2) Select "Edit profile" at the top right of the screen > Click "Email" under Contact details
3) Edit your email address
Similarly you can follow the same steps to change your mobile number.