A recent dispute between two taxi companies confirms that a telephone number is not property and is not owned by the telco customer.
"Relevantly, the terms confirm that the customer does not own or have any legal interest or goodwill in any telephone number issued to the customer. The terms also permit the customer to “transfer” a telephone number to another person with the prior consent of Telstra."
Manly Warringah Cabs (Trading) Co-operative Limited v Sydney Taxis Pty Ltd, in the matter of Sydney Taxis Pty Ltd (No 2)  FCA 1336
Compare this domain name decision: Multi-National Concepts Pty Ltd v. 1300 Directory Pty Ltd