Hey guys I don't know what the problem is here I've tried searching and finding the solution but I can't seem to find the root of the problem.
So my iphone is a 3gs old bootrom and I've recently upgraded from 4.0.3 to 5.1.1(9B206) using sn0wbreeze and hacktivated it using the ultrasn0w+fix
baseband is 05.13.04
And everything's working fine, the data, the mms but the imessage for some reason half the time it doesn't show up as an option to my iphone contacts and when it does it says "iMessage not delivered" with the red exclaimation mark.

in the messages section of settings I have iMessage set to on and it says "iMessages can be sent between iPhone, iPad and iPod touch."
I'm using carrier simple mobile and I also have wifi available when this error happens and I'm on the edge network as well. So the internet access is there. My MMS is working as well.

So I really don't know why iMessages aren't working :/ Thanks for reading I hope someone might know what's going on here.