NBN phone unable to make calls but has dial tone

[AGT]

Unable to make calls local or national, for about a week. Internet works.

After dialling 5 digits = engaged signal.
I recently changed modem password. My modem says:

Telephone Status: Telephone service unavailable. Please check your account settings or register a new number.

[Anonymous]

Hi @AGT,

Let us help check what causing issues with the landline and get this sorted out Could you shoot us a PM with your details.

Regards,

Unable to make calls local or national, for about a week. Internet works.

After dialling 5 digits = engaged signal.
I recently changed modem password. My modem says:

Telephone Status: Telephone service unavailable. Please check your account settings or register a new number.