curl --request POST \
  --url https://coreapi.io/api/customer/subscriptions/{id}/plan-tier-preview \
  --header 'Authorization: Bearer <token>' \
  --header 'Content-Type: application/json' \
  --data '
{
  "planTierId": "f5ece259-08ea-77a4-8bd9-9f3a9ed9e246",
  "items": []
}
'

import requests

url = "https://coreapi.io/api/customer/subscriptions/{id}/plan-tier-preview"

payload = {
    "planTierId": "f5ece259-08ea-77a4-8bd9-9f3a9ed9e246",
    "items": []
}
headers = {
    "Authorization": "Bearer <token>",
    "Content-Type": "application/json"
}

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

print(response.text)

const options = {
  method: 'POST',
  headers: {Authorization: 'Bearer <token>', 'Content-Type': 'application/json'},
  body: JSON.stringify({planTierId: 'f5ece259-08ea-77a4-8bd9-9f3a9ed9e246', items: []})
};

fetch('https://coreapi.io/api/customer/subscriptions/{id}/plan-tier-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://coreapi.io/api/customer/subscriptions/{id}/plan-tier-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([
    'planTierId' => 'f5ece259-08ea-77a4-8bd9-9f3a9ed9e246',
    'items' => [
        
    ]
  ]),
  CURLOPT_HTTPHEADER => [
    "Authorization: Bearer <token>",
    "Content-Type: application/json"
  ],
]);

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

curl_close($curl);

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

{
  "creditAmount": "14.50",
  "chargeAmount": "24.50",
  "currency": "EUR",
  "effectiveAt": "2023-11-07T05:31:56Z",
  "recurringTotal": {
    "netAmount": "49.00",
    "taxAmount": "9.31",
    "grossAmount": "58.31",
    "currency": "EUR"
  },
  "warnings": [
    "active_discount_will_be_lost"
  ]
}

{
  "status": 404,
  "type": "PLAN__NOT_FOUND",
  "title": "An error occurred",
  "detail": "Plan not found."
}

{
  "status": 404,
  "type": "PLAN__NOT_FOUND",
  "title": "An error occurred",
  "detail": "Plan not found."
}

{
  "status": 404,
  "type": "PLAN__NOT_FOUND",
  "title": "An error occurred",
  "detail": "Plan not found."
}

{
  "status": 422,
  "type": "https://tools.ietf.org/html/rfc2616#section-10",
  "title": "Validation Failed",
  "violations": [
    {
      "propertyPath": "tiers[0].name",
      "message": "This value should not be blank.",
      "code": "<string>"
    }
  ]
}