Only in limited cases: if you have attended a bulk-billing practice in person within the last 12 months, you are eligible for phone or telehealth calls, which can include medical certificates. There are some exemption categories that mean you can access bulk-billing such as living in a declared disaster area or in a very remote location, but, obviously most people do not qualify for these exemptions.
Telehealth services that advertise “bulk billing” for medical certificates online will still charge you a private fee when you fail their eligibility check.