Major problem with texting for me (involves iPhone, imessage)

[Ya_Bish]

So I recently put my sim into a new iphone just for fun to see how it is. I am back on my GS3 now, but I have a huge problem.

I am not getting texts from everyone again. I am from non apple people and even some of my iphone friends, but not from a lot of iphone friends I have. I've tested it with them, they said they are getting a "message cant be delivered" thing.

I turned off iMessage, reset that iPhone and all. WTF.

Help
Thanks.