Vonage had a Free outgoing fax service (vfax) for subscriber.
Is it still available, and what is the web site.
If they do, it's thoroughly hidden.
Going to the old site address I used to use (https://v-fax.vonage.com) produces a security warning from my PC's software that its authentication fails, that it is a site associated with identity theft.
I guess if there is a free service that is the free trail period offered after you subscribe for the service.