In the parameters array of objects, you're missing the parameter_name, you are just sending type and text but it should be like this according to the documentation:

"parameters": [ { "type": "text", "paramter_name": "customer_name", "text": "John" }, { "type": "text", "parameter_name": "order_id", "text": "9128312831" }
]

Also, if your parameter type is text, then make sure your text is double quoted, like this:

"parameters": [ { "type": "text", "parameter_name": "name_of_your_parameter_in_the_template", "text": "John Doe" // Replace with user's first name }, { "type": "text", "parameter_name": "name_of_your_parameter_in_the_template", "text": "9999" // Replace with order ID }, { "type": "text", "parameter_name": "name_of_your_parameter_in_the_template", "text": "Confirmed" // Replace with order status }, { "type": "text", "text": "199" // Replace with order amount } ]