Is there an app for chatting?

So i have gmail and i chat with people on there. The problem is I can only chat when i'm on the computer. I want to be able to talk to them offline using my iphone. I was wondering if there was an app that would allow me to do that and send me notifications when i get a chat. If there's what is the app called

Can I flash my AT&T iPhone 4 to Cricket Wireless?

I've tried researching this, but I keep getting conflicting answers. I've called Cricket customer service and they gave me addresses to full-service, corporate stores that do it; however, when I arrived the sales rep had no clue what he was talking about and kept contradicting himself. I've also looked on the internet, but again I get conflicting answers. Please help!

Added (1). @Zachary - How do I unlock it?

I lost all my iPhone contacts after updating?

The last time I updated my iPhone I ended up losing all of my contacts! However I can still search for peoples names on my messages and my contacts name is there!
This obviously means that my contacts are still in the phones system, but for some strange reason they have disappeared from my contact list.

I still have all my photos and all my messages.
Any help will be great.

How to tell if an iphone is stolen?

I had an Iphone 4s and then it broke so I had to use my old iphone 3g which sucks. I saw an add on craigslist and I was wondering how do you know if a phone is stolen before I buy it? I have my old iphone 4s sim card which is smaller than the iphone 3g sim chip so I was going to put it in to see if it worked but I don't know if you can tell by that or not. So basically before I buy this phone how do I tell if its stolen? I don't want to buy a stolen iphone!

When will the iPhone either 5s or 6 come out?

I know it comes out this year, but especially month and the date would be really helpful! Also please tell me what Apple is going to call the next major iPhone! I'm asking this because I have t-Mobile and my dad said that he would get me the iPhone once iphone 5s/6 comes out.

Iphone 3gs won't charge unless turned off?

I have a iphone 3gs and the other day i broke the lcd screen and the digitizer, but the phone still synced
with itunes then when i went to bed and put it on charge it never beeped or the lightning bolt never appeared, but i noticed it would only charge when powered off. And now itunes does not detect the phone and i get a windows does not recognise connected device error, i have also tried in dfu mode, i also seem to lose service, the phone is jailbroken so can't restore from on the device and i have no warranty so can't send it to apple. Do you think if i replace the charging dock it will charge again or not. Please if this has happened to you or if you have any suggestions can you share your advice all help will be truly appreciated

Instagram doesn't let me upload photos or see my profile?

It updates my feed but every time I upload a photo it goes straight to "Failed" and when I try to see my profile the error msg "Couldn't refresh feed" comes up. I've restarted my iphone, I've deleted the app twice, I've restarted my internet. Nothing fixes it. Is there anything else I'm not trying?