Remove old phone number from Google 2-factor Authentication

To remove your old phone number select your initial next to the 1590 Trust logo 

Select 'Manage your Google Account'

Select 'Security' from the left menu

Under heading 'How to sign in to Google' select '2-step Verification'

Re-enter your password if prompted.

Select '>' to the right of 'Voice or text message'

If you have the bin icon next to your old phone number select it to delete your old phone number and then select 'Add a backup 2-step verification phone' to add your new number.

Follow the onscreen instructions to add your new phone number.

If you don't have the bin icon select 'Add a backup 2-step verification phone' and follow the onscreen instructions to add your new number. Once added, click the bin icon to delete your old number.