BNZ has launched its home loan support service. They are handling queries via an application form on their website.
Excerpt from BNZ website. Updated 1 April 2020.
Support for homeowners
You could be eligible for a home loan repayment deferral for up to six months, or ‘interest only’ payments for up to 12 months, if your income has been affected by COVID-19. Complete our application form and we’ll get in touch with you to talk through the next steps.
Due to COVID-19 we are experiencing a significant increase in enquiries, which means the wait is longer than we’d like. We’re working through these and aiming to get back to you within five business days to discuss your home loan enquiry.
To understand your borrowing power calculations from BNZ and other banks check out this page about mortgage calculations.