I cannot access my account

When I log in to my account a message appears saying 'it looks like someone else is using your account'. I have filled out the questionnaire three times only for it to be rejected due to insufficient information. A lot of the questions I really don't know the answer to e.g the addresses of recent contacts by email. I rarely send emails and so cannot remember any adresses or contacts. Also I cannot receive a code by text or phone because the number that is displayed is not one I am using or recognise. Surely there's got to be another way of getting my account back? Any help will be much appreciated thanks.