My iPhone 4 won't send iMessage and I'm connected to Wi-Fi?

My mom turned my phone off because I didn't do my summer projects on time. But I can still text people with iPhones only if I have Wi-Fi but sometimes they won't send and I can't receive them. But my Internet and everything works fine. What fixes this?

Assuming you have updated to iOS 6.iMessage also uses your phone number to send and receive messages. When your cellular network is deactivated messages will not send if they solely rely on your number. To solve this go to settings, messages, send and receive. Once you are there change everything to your email address.