Twilio sets no additional restriction for Global SMS on trial accounts. You can send international messages from your trial account as long as you verify the following:

• Make sure your trial phone number is an SMS-enabled phone number that supports Global SMS. Note that some Twilio numbers only carry voice capability and cannot be used to send messages. Also some SMS-enabled phone numbers are labeled as domestic-only (eg, local numbers in UK), and thus cannot be used to send messages to other countries. 
• Review the SMS Geo Permissions page and make sure permission to the target country is enabled. For example, if you are sending messages to France, make sure the check box next to France is checked. 
• As Twilio only allows sending messages to verified numbers with a trial account, make sure you verify the international phone number you're sending to by going to the Verified Caller IDs page. Check out other trial restrictions here, or upgrade your Twilio account.

Now try out your first message by using the API Explorer.