This endpoint changes the package of the vPanel user account associated with provided information.
Your package name must be fully lowercase since otherwise the user will get the "Client is not allocated to a package" package which has the maximum resources.
curl -X POST -u username:password -d "user=example&pkg=myawesomeplan" "https://panel.myownfreehost.net/json-api/changepackage.php"
For some reason iFastNet decided it was a good idea to return XML on a JSON API endpoint. This is why the response is in XML.
The above request returns XML structured like the following:
<changepackage><result><rawout></rawout><status>1</status><statusmsg>Account Upgrade/Downgrade Complete for asdfasdf</statusmsg></result></changepackage>