Here are the rules.
1. Establish service with Sprint (it cannot be an ASL (Account Spending Limit) account)
2. Maintain service with Sprint for 90 days
3. Pay your bill on time
4. Call Sprint, ask for international unlock
If you CANNOT meet ANY of these requirements, Sprint will NOT unlock your iPhone for international use.
There is NO third party unlock, either for international or domestic use. ONLY Sprint can unlock your iPhone for international use.
If you have purchased already and cannot meet #1 and #2, congratulations you have just bought yourself an expensive iPod Touch!