To send SMS worldwide you must make sure to-
1. comply with the respective Sender ID rules of the country you are sending SMS to as there are different Sender ID registration processes for different countries. Refer to this article to check these rules.
2. always add the correct country code to the mobile numbers while sending the SMS (e.g. 919999999999)
Note- You don't need to add a '+' or '-' sign or include any space before the number.