How to write wordPress Hook?

I followed this instruction to write a hook for form: 3rd party integration plugin from the author
(https://github.com/zaus/forms-3rdparty-integration#hooks)

add_action(‘Forms3rdPartyIntegration_service_a#’, $response, $param_ref);

hook for each service, indicated by the # – this is given in the ‘Hooks’ section of each service
provide a function which takes $response, &$results as arguments

allows you to perform further processing on the service response,
and directly alter the processing results, provided as array(‘success’=>false, ‘errors’=>false, ‘attach’=>”, ‘message’ => ”);

success = true or false – change whether the service request is treated as “correct” or not
errors = an array of error messages to return to the form
attach = text to attach to the end of the email body

message = the message notification shown (from CF7 ajax response) below the form
note that the basic “success condition” may be augmented here by post processing

I came up with this function and added it on my functions.php but it doesn’t work. Am I doing something wrong?

if(!class_exists('Cf73rdParty_custom_message')){

class Cf73rdParty_custom_message {

public function __construct(){
//actions require 2 parameters: 3rd-party response, results placeholders
///NOTE: customize this hook name to match your Service (in the admin settings)
add_action('Forms3rdPartyIntegration_service_a7', array(&$this, 'adjust_response'), 10, 2);
}//-- function __construct

public function adjust_response($response, &$results) {


    if(!empty($response['body'])){
            if($response['body'] = 'CustomerExists');
            {       $response['success'] = 'false';
                    $results['errors'] = array('User already exists');
                    $results['message'] = 'A trial for this customer already exists';
            }

    }

}
}


}

$Cf73rdParty_custom_message_ins = new Cf73rdParty_custom_message(); // attach hook