@Amit . The router is not locked to TPG. The problem might be with the VLAN ID difference between TPG and Tangerine.
|VLAN ID Settings:|
|NBN ordered 1st June 2017 onwards||Disabled / not active|
|NBN ordered pre-1st June 2017||VLAN ID 100|
You need to disable the VLAN function or change it to 100.