// После создания заказа
AddEventHandler("sale", "OnOrderAdd", "SendSmsOrder");
function SendSmsOrder($arFields) 
{
    $ch = curl_init("https://sms.ru/sms/send");
    curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
    curl_setopt($ch, CURLOPT_TIMEOUT, 30);
    curl_setopt($ch, CURLOPT_POSTFIELDS, array(
    "api_id"        =>  "_____API_ID________",
    "to"            =>  "_____PHONE_________",
    "text"      =>  iconv("utf-8","windows-1251","___TEXT_____")
    ));
    $body = curl_exec($ch);
    curl_close($ch); 
    pr($body);
}