curl --request POST \
  --url https://us.api.flexprice.io/v1/subscriptions/{id}/change/preview \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "billing_cadence": "RECURRING",
  "target_plan_id": "<string>",
  "billing_period_count": 123,
  "metadata": {}
}
'

import requests

url = "https://us.api.flexprice.io/v1/subscriptions/{id}/change/preview"

payload = {
    "billing_cadence": "RECURRING",
    "target_plan_id": "<string>",
    "billing_period_count": 123,
    "metadata": {}
}
headers = {
    "x-api-key": "<api-key>",
    "Content-Type": "application/json"
}

response = requests.post(url, json=payload, headers=headers)

print(response.text)

const options = {
  method: 'POST',
  headers: {'x-api-key': '<api-key>', 'Content-Type': 'application/json'},
  body: JSON.stringify({
    billing_cadence: 'RECURRING',
    target_plan_id: '<string>',
    billing_period_count: 123,
    metadata: {}
  })
};

fetch('https://us.api.flexprice.io/v1/subscriptions/{id}/change/preview', options)
  .then(res => res.json())
  .then(res => console.log(res))
  .catch(err => console.error(err));

<?php

$curl = curl_init();

curl_setopt_array($curl, [
  CURLOPT_URL => "https://us.api.flexprice.io/v1/subscriptions/{id}/change/preview",
  CURLOPT_RETURNTRANSFER => true,
  CURLOPT_ENCODING => "",
  CURLOPT_MAXREDIRS => 10,
  CURLOPT_TIMEOUT => 30,
  CURLOPT_HTTP_VERSION => CURL_HTTP_VERSION_1_1,
  CURLOPT_CUSTOMREQUEST => "POST",
  CURLOPT_POSTFIELDS => json_encode([
    'billing_cadence' => 'RECURRING',
    'target_plan_id' => '<string>',
    'billing_period_count' => 123,
    'metadata' => [
        
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Content-Type: application/json",
    "x-api-key: <api-key>"
  ],
]);

$response = curl_exec($curl);
$err = curl_error($curl);

curl_close($curl);

if ($err) {
  echo "cURL Error #:" . $err;
} else {
  echo $response;
}

package main

import (
	"fmt"
	"strings"
	"net/http"
	"io"
)

func main() {

	url := "https://us.api.flexprice.io/v1/subscriptions/{id}/change/preview"

	payload := strings.NewReader("{\n  \"billing_cadence\": \"RECURRING\",\n  \"target_plan_id\": \"<string>\",\n  \"billing_period_count\": 123,\n  \"metadata\": {}\n}")

	req, _ := http.NewRequest("POST", url, payload)

	req.Header.Add("x-api-key", "<api-key>")
	req.Header.Add("Content-Type", "application/json")

	res, _ := http.DefaultClient.Do(req)

	defer res.Body.Close()
	body, _ := io.ReadAll(res.Body)

	fmt.Println(string(body))

}

HttpResponse<String> response = Unirest.post("https://us.api.flexprice.io/v1/subscriptions/{id}/change/preview")
  .header("x-api-key", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"billing_cadence\": \"RECURRING\",\n  \"target_plan_id\": \"<string>\",\n  \"billing_period_count\": 123,\n  \"metadata\": {}\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://us.api.flexprice.io/v1/subscriptions/{id}/change/preview")

http = Net::HTTP.new(url.host, url.port)
http.use_ssl = true

request = Net::HTTP::Post.new(url)
request["x-api-key"] = '<api-key>'
request["Content-Type"] = 'application/json'
request.body = "{\n  \"billing_cadence\": \"RECURRING\",\n  \"target_plan_id\": \"<string>\",\n  \"billing_period_count\": 123,\n  \"metadata\": {}\n}"

response = http.request(request)
puts response.read_body

{
  "change_type": "upgrade",
  "current_plan": {
    "description": "<string>",
    "id": "<string>",
    "lookup_key": "<string>",
    "name": "<string>"
  },
  "effective_date": "2023-11-07T05:31:56Z",
  "metadata": {},
  "new_billing_cycle": {
    "billing_anchor": "2023-11-07T05:31:56Z",
    "billing_cadence": "RECURRING",
    "billing_period": "MONTHLY",
    "billing_period_count": 123,
    "period_end": "2023-11-07T05:31:56Z",
    "period_start": "2023-11-07T05:31:56Z"
  },
  "next_invoice_preview": {
    "currency": "<string>",
    "due_date": "2023-11-07T05:31:56Z",
    "line_items": [
      {
        "amount": "<string>",
        "description": "<string>",
        "is_proration": true,
        "period_end": "2023-11-07T05:31:56Z",
        "period_start": "2023-11-07T05:31:56Z",
        "quantity": "<string>",
        "unit_price": "<string>"
      }
    ],
    "subtotal": "<string>",
    "tax_amount": "<string>",
    "total": "<string>"
  },
  "proration_details": {
    "charge_amount": "<string>",
    "charge_description": "<string>",
    "credit_amount": "<string>",
    "credit_description": "<string>",
    "currency": "<string>",
    "current_period_end": "2023-11-07T05:31:56Z",
    "current_period_start": "2023-11-07T05:31:56Z",
    "days_remaining": 123,
    "days_used": 123,
    "net_amount": "<string>",
    "proration_date": "2023-11-07T05:31:56Z"
  },
  "subscription_id": "<string>",
  "target_plan": {
    "description": "<string>",
    "id": "<string>",
    "lookup_key": "<string>",
    "name": "<string>"
  },
  "warnings": [
    "<string>"
  ]
}

{
  "code": "http_client_error",
  "http_status_code": 123,
  "message": "<string>"
}

{
  "code": "http_client_error",
  "http_status_code": 123,
  "message": "<string>"
}

{
  "code": "http_client_error",
  "http_status_code": 123,
  "message": "<string>"
}