To Change your account phone number, log into your account and select Account Settings. (Please note this can only be done via a Desktop/Laptop computer)
Click Edit beside the Mobile number Field. Enter in your new number and click Save Changes.
A verification code will be sent to your new number to complete the process.
If you already have registered a phone number to your account, and you no longer have access to this number, then you will need to contact Customer Support in order to have the number changed. You can send an email to support@daft.ie to request the change.