Move compatible voice workflows in measured steps.

// npm install twilio
const twilio = require('twilio');
const RequestClient = require('twilio/lib/base/RequestClient');

class VoiceTelClient extends RequestClient {
	async request(opts) {
		opts.uri = opts.uri.replace(
			/https:\/\/[^/]+\.twilio\.com/,
			'https://voiceml.voicetel.com'
		);
		return super.request(opts);
	}
}

const client = twilio(
	process.env.VOICETEL_ACCOUNT_SID,
	process.env.VOICETEL_API_KEY,
	{ httpClient: new VoiceTelClient() }
);

const call = await client.calls.create({
	to:   '+18005551234',
	from: '+18005550000',
	url:  'https://your-app/voicemarkup',
});
console.log(call.sid);

# pip install twilio
import os
from twilio.rest import Client
from twilio.http.http_client import TwilioHttpClient

class VoiceTelClient(TwilioHttpClient):
	def request(self, method, url, *args, **kwargs):
		url = url.replace(
			'https://api.twilio.com',
			'https://voiceml.voicetel.com',
		)
		return super().request(method, url, *args, **kwargs)

client = Client(
	os.environ['VOICETEL_ACCOUNT_SID'],
	os.environ['VOICETEL_API_KEY'],
	http_client=VoiceTelClient(),
)

call = client.calls.create(
	to='+18005551234',
	from_='+18005550000',
	url='https://your-app/voicemarkup',
)
print(call.sid)

// go get github.com/twilio/twilio-go
package main

import (
	"net/http"
	"net/url"
	"os"
	"strings"

	"github.com/twilio/twilio-go"
	"github.com/twilio/twilio-go/client"
	openapi "github.com/twilio/twilio-go/rest/api/v2010"
)

type voiceTelClient struct{ inner *http.Client }

func (c *voiceTelClient) Do(req *http.Request) (*http.Response, error) {
	if strings.HasSuffix(req.URL.Host, ".twilio.com") {
		rewritten, _ := url.Parse("https://voiceml.voicetel.com" +
			req.URL.RequestURI())
		req.URL = rewritten
		req.Host = rewritten.Host
	}
	return c.inner.Do(req)
}

func main() {
	httpClient := &voiceTelClient{inner: http.DefaultClient}

	tw := twilio.NewRestClientWithParams(twilio.ClientParams{
		Username: os.Getenv("VOICETEL_ACCOUNT_SID"),
		Password: os.Getenv("VOICETEL_API_KEY"),
		Client: &client.Client{
			HTTPClient: httpClient,
			Credentials: client.NewCredentials(
				os.Getenv("VOICETEL_ACCOUNT_SID"),
				os.Getenv("VOICETEL_API_KEY"),
			),
		},
	})

	params := &openapi.CreateCallParams{}
	params.SetTo("+18005551234")
	params.SetFrom("+18005550000")
	params.SetUrl("https://your-app/voicemarkup")

	call, err := tw.Api.CreateCall(params)
	if err != nil { panic(err) }
	println(*call.Sid)
}

// dotnet add package Twilio
using System;
using System.Net.Http;
using System.Threading.Tasks;
using Twilio;
using Twilio.Clients;
using Twilio.Http;
using Twilio.Rest.Api.V2010.Account;

public class VoiceTelHttpClient : SystemNetHttpClient
{
	public VoiceTelHttpClient(HttpClient http) : base(http) { }

	public override Response MakeRequest(Request request)
	{
		var rewritten = request.Url.ToString().Replace(
			"https://api.twilio.com",
			"https://voiceml.voicetel.com");
		request.Url = new Uri(rewritten);
		return base.MakeRequest(request);
	}
}

class Program
{
	static async Task Main()
	{
		var http = new HttpClient();
		TwilioClient.Init(
			Environment.GetEnvironmentVariable("VOICETEL_ACCOUNT_SID"),
			Environment.GetEnvironmentVariable("VOICETEL_API_KEY"),
			new VoiceTelHttpClient(http));

		var call = await CallResource.CreateAsync(
			to:   new Twilio.Types.PhoneNumber("+18005551234"),
			from: new Twilio.Types.PhoneNumber("+18005550000"),
			url:  new Uri("https://your-app/voicemarkup"));

		Console.WriteLine(call.Sid);
	}
}

// composer require twilio/sdk
<?php
require __DIR__ . '/vendor/autoload.php';

use Twilio\Rest\Client;
use Twilio\Http\CurlClient;
use Twilio\Http\Response;

class VoiceTelClient extends CurlClient {
	public function request(
		string $method, string $url, array $params = [],
		array $data = [], array $headers = [],
		?string $user = null, ?string $password = null,
		?int $timeout = null
	): Response {
		$url = preg_replace(
			'#https://[^/]+\.twilio\.com#',
			'https://voiceml.voicetel.com',
			$url);
		return parent::request(
			$method, $url, $params, $data, $headers,
			$user, $password, $timeout);
	}
}

$client = new Client(
	getenv('VOICETEL_ACCOUNT_SID'),
	getenv('VOICETEL_API_KEY'),
	null, null,
	new VoiceTelClient()
);

$call = $client->calls->create(
	'+18005551234',
	'+18005550000',
	['url' => 'https://your-app/voicemarkup']
);
echo $call->sid . "\n";

// Gradle: implementation 'com.twilio.sdk:twilio:10.+'
import com.twilio.Twilio;
import com.twilio.http.NetworkHttpClient;
import com.twilio.http.Request;
import com.twilio.http.Response;
import com.twilio.http.TwilioRestClient;
import com.twilio.rest.api.v2010.account.Call;
import com.twilio.type.PhoneNumber;
import java.net.URI;

public class VoiceTelApp {
	static class VoiceTelClient extends NetworkHttpClient {
		@Override
		public Response makeRequest(Request request) {
			String original = request.constructURL().toString();
			String rewritten = original.replaceFirst(
				"https://[^/]+\\.twilio\\.com",
				"https://voiceml.voicetel.com");
			Request copy = new Request(request.getMethod(), rewritten);
			request.getQueryParams().forEach(
				(k, v) -> v.forEach(val -> copy.addQueryParam(k, val)));
			request.getPostParams().forEach(
				(k, v) -> v.forEach(val -> copy.addPostParam(k, val)));
			return super.makeRequest(copy);
		}
	}

	public static void main(String[] args) {
		String sid = System.getenv("VOICETEL_ACCOUNT_SID");
		String key = System.getenv("VOICETEL_API_KEY");
		Twilio.init(sid, key);
		Twilio.setRestClient(new TwilioRestClient.Builder(sid, key)
			.httpClient(new VoiceTelClient()).build());

		Call call = Call.creator(
			new PhoneNumber("+18005551234"),
			new PhoneNumber("+18005550000"),
			URI.create("https://your-app/voicemarkup")
		).create();

		System.out.println(call.getSid());
	}
}

# gem install twilio-ruby
require 'twilio-ruby'

class VoiceTelHttpClient < Twilio::HTTP::Client
	def request(method, host, port, uri, params, data, headers,
				auth, timeout, allow_redirects)
		rewritten = uri.sub(
			%r{https://[^/]+\.twilio\.com},
			'https://voiceml.voicetel.com'
		)
		super(method, 'voiceml.voicetel.com', port,
			  rewritten, params, data, headers,
			  auth, timeout, allow_redirects)
	end
end

client = Twilio::REST::Client.new(
	ENV['VOICETEL_ACCOUNT_SID'],
	ENV['VOICETEL_API_KEY'],
	nil, nil,
	VoiceTelHttpClient.new
)

call = client.calls.create(
	to:   '+18005551234',
	from: '+18005550000',
	url:  'https://your-app/voicemarkup'
)
puts call.sid