iphone5c not active whit itunes , help me ... iPHONE 5C IMEI : 357996053152342

I have a been a source iphone5c when you donate to VIETNAM! but do not know which network is being locked because the check is reported that AT & T but not active, I have tried to use the Sprint network sim but still not ok! Can you please help me active. I apologize for not being able to speak English, so thanks to google send me this. Please help me with this because I liked the iphone. thank you.