In order to make calls abroad with your Twilio number, you will have to enable International Dialing with Twilio as a phone provider. For this, you will have to sumbit a request to Twilio support team. 
You will have to enable this selecting which countries you want to enable it for

However, this only works for voice. If you are using Geographic numbers, you won't be able to send SMS. For this, you will need another number that supports SMS messages internationally.