All HTTP requests require SMS API Account Credentials. If you are testing the demo for the first time, SMSGatewayCenter.com offers Free SMS Credits upto 5 units to test delivery and other parameters. In some cases, for API users they may require additional credits to analyze the API response.
If users require a Test Account to test further, then they can request our Accounts Manager to enable one. Once enabled, few credits will be added to your live account to send HTTP requests. All the process will remain the same, but it will not be sent to the operators to deliver the text message.
You can view the DLR, messsage response, API validations, Error codes, Success codes, etc.,
If you have further clarification, please contact your respective Accounts Manager.