IPhone can't receive iMessages but it can send them?

So today, my iPhone said 'waiting for activation'. I think I managed to fix that part.

Now, I can send iMessages but can't receive them, I can receive iMessages on my Mac, but not my phone.

You have to either be connected to Wi-Fi or have Internet on your phone to use iMessage, the person who you sent the iMessage to could have their iMessage turned off