So First, Login…
Next go up next to your name/home area and press the arrow.
You’ll get a drop down menu, now select “Account Settings”
Next Click on “Mobile” in the top left column area.
Now remove all the numbers you want off the account (by pressing the “remove” button. After than press the “+ add another mobile phone number to the account” link. Follow the directions from there.
Now if you do this and the number you wanted to remove is not here, then simply go to your profile by clicking “Your Name” at the top right of the page and go to “About” section and press edit on the “Info” area to change address/phone info.