Iphone 4s won't send imessage
I have a iphone 4s. My carrier is fido. When i'm at home, i'm able to send imessages and text without a problem. But when i'm out, it won't send imeessages even though i have full bars, and only sometimes it send text. I tried turning on/off airplane mode, but that works for like 20 seconds. I try cloising the app and opening again and even turining off my phone but nothing works. Please if you have any idea what can help me, or how to fix this, thanks a lot!