curl --request POST \
  --url https://rest-api.smsmngr.com/v1/billing/set \
  --header 'Content-Type: application/json' \
  --header 'x-api-key: <api-key>' \
  --data '
{
  "billing_id": "1234",
  "name": "ACME s.r.o.",
  "email": "invoicing@acme.example",
  "street": "Ulice 1",
  "city": "Praha",
  "zip": "11000",
  "country": "cz",
  "company_id": "12345678",
  "company_vat": "CZ12345678"
}
'

import requests

url = "https://rest-api.smsmngr.com/v1/billing/set"

payload = {
    "billing_id": "1234",
    "name": "ACME s.r.o.",
    "email": "invoicing@acme.example",
    "street": "Ulice 1",
    "city": "Praha",
    "zip": "11000",
    "country": "cz",
    "company_id": "12345678",
    "company_vat": "CZ12345678"
}
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_id: '1234',
    name: 'ACME s.r.o.',
    email: 'invoicing@acme.example',
    street: 'Ulice 1',
    city: 'Praha',
    zip: '11000',
    country: 'cz',
    company_id: '12345678',
    company_vat: 'CZ12345678'
  })
};

fetch('https://rest-api.smsmngr.com/v1/billing/set', 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://rest-api.smsmngr.com/v1/billing/set",
  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_id' => '1234',
    'name' => 'ACME s.r.o.',
    'email' => 'invoicing@acme.example',
    'street' => 'Ulice 1',
    'city' => 'Praha',
    'zip' => '11000',
    'country' => 'cz',
    'company_id' => '12345678',
    'company_vat' => 'CZ12345678'
  ]),
  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://rest-api.smsmngr.com/v1/billing/set"

	payload := strings.NewReader("{\n  \"billing_id\": \"1234\",\n  \"name\": \"ACME s.r.o.\",\n  \"email\": \"invoicing@acme.example\",\n  \"street\": \"Ulice 1\",\n  \"city\": \"Praha\",\n  \"zip\": \"11000\",\n  \"country\": \"cz\",\n  \"company_id\": \"12345678\",\n  \"company_vat\": \"CZ12345678\"\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://rest-api.smsmngr.com/v1/billing/set")
  .header("x-api-key", "<api-key>")
  .header("Content-Type", "application/json")
  .body("{\n  \"billing_id\": \"1234\",\n  \"name\": \"ACME s.r.o.\",\n  \"email\": \"invoicing@acme.example\",\n  \"street\": \"Ulice 1\",\n  \"city\": \"Praha\",\n  \"zip\": \"11000\",\n  \"country\": \"cz\",\n  \"company_id\": \"12345678\",\n  \"company_vat\": \"CZ12345678\"\n}")
  .asString();

require 'uri'
require 'net/http'

url = URI("https://rest-api.smsmngr.com/v1/billing/set")

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_id\": \"1234\",\n  \"name\": \"ACME s.r.o.\",\n  \"email\": \"invoicing@acme.example\",\n  \"street\": \"Ulice 1\",\n  \"city\": \"Praha\",\n  \"zip\": \"11000\",\n  \"country\": \"cz\",\n  \"company_id\": \"12345678\",\n  \"company_vat\": \"CZ12345678\"\n}"

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