In particular, if you are interested in using Visa Direct, see the top few paragraphs that are shaded in yellow that discuss the requirements to use Visa Direct.
After having read the documentation, if you meet those requirements, then please click through the link in those paragraphs to the Visa Direct Program Implementation Questionnaire, fill it out, and submit to the email address listed on that form.
If you're interested in B2B payments, we use the B2B APIs for automating payments. Also, B2B Connect APIs are only available to Banks and their authorized technology providers. B2B Connect APIs allow payments between corporates that are routed via banks to the platform.