The given `SendAsync` method in the example is an extension method to send sms with primitive paremeters, it basicly creates `SmsMessage` object and pass it. You can also use the default `SendAsync` method which requires `SmsMessage` object.
> `IEmailSender` is the suggested way to send emails, since it makes your code provider independent.
> `ISmsSender` is the suggested way to send SMS, since it makes your code provider independent.