How do I set up multiple extensions without having multiple users?

We only have 2 users in our office but would like to have multiple extensions for a number of reasons. These include 1) More than 2 handsets at various locations throughout our business. While I am the only one that would answer them, the other user would like to be able to transfer calls to me wherever I am 2) Have separate call in line with different voice mail for contractors to check job status or leave messages 3) Different voice mail lines for clients to leave messages depending on their needs. 4) After hours extension that rings when others are turned off So how do we set up additional extensions without creating extra users?

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