How do I block another user from contacting me?

Desktop

In the lists, there is a little cross on the top right of the user's photo. If you click on that cross then you have options to remove them from the lists, block them or report them. When viewing their profile on the top right are three icons and the one on the far right blocks the user. To add the user directly to the blocked list and also remove users from the lists go to the following page:-

Under "my account" > "[privacy settings]"

Mobile

View their profile and on the top right is a down arrow which drops down a list of options. Choose the "block" option.