[DE-932] Rename Chargify API

Author: michalpierog

README.md

@@ -7,7 +7,7 @@ Maxio Advanced Billing (formerly Chargify) provides an HTTP-based API that confo
 One of the many reasons to use Advanced Billing is the immense feature set and surrounding community [client libraries](page:development-tools/client-libraries).
 The Maxio API returns JSON responses as the primary and recommended format, but XML is also provided as a backwards compatible option for Merchants who require it.
 
-### Steps to make your first Maxio Chargify API call
+### Steps to make your first Maxio Advanced Billing API call
 
 1. [Sign-up](https://app.chargify.com/signup/maxio-billing-sandbox) or [log-in](https://app.chargify.com/login.html) to your [test site](https://maxio.zendesk.com/hc/en-us/articles/24250712113165-Testing-Overview) account.
 2. [Setup and configure authentication](https://maxio.zendesk.com/hc/en-us/articles/24294819360525-API-Keys) credentials.