Perhaps I wasn't clear enough.
You do first sign up for service with Callcentric or Anveo, independently of the OBiTALK portal. After you have done that, and you have your SIP username and SIP password, you click on the link I mentioned, and then just enter the username and password you already obtained. Obihai isn't involved in any financial transaction or related provider tasks. It's just providing pre-built configurations tailored to the various SPs on the list.
Example: I go to Callcentric, and set up service with them. I set up my password. I then log onto the OBiTALK portal, click SP3, and scroll down to the bottom of the page and click OBiTALK Compatible Service Providers. On the next page, I click "Callcentric". It then opens a form for me to fill in my Callcentric user ID and SIP password, and I also check-mark the box to "Use This Service for Emergency 911 Calls". Optionally, I enter a local area code, and then click "Submit". The portal configures SP3 to use my Callcentric account.