Mitel 5330 IP Phone SIP and Firmware issues

Hi all

We have been asked to connect a Mitel 5330 IP Phone but can’t get it to boot into SIP mode by using the *7 whilst booting method.

We think we need a firmware upgrade but can’t find it anywhere?

Can anyone help or advise?

Has anyone any experience of Mitel phones on SIP? The phone build quality is excellent.

Many thanks