IPhone 4 issue / no one can hear me?

So lately my phone's not working right. I can hear people fine but no one can hear me. I've played music so I know the speakers are working, even voice memo works! But no one can hear me. Turned it on/off about a 1000 times today! PLEAE Help! Any one know?

Can I sell my iPhone 5s under contract AT&T?

I bought an unlocked iPhone 6, swapped the sim out of my old 5s. Everything is working fine I just want to know if I can sell the 5s without voiding my contract or affecting my plan? I tried to talk to a represenitive at ATT but they didn't quite understand what I was asking.

Does deleting iCloud off one device deletes my account forver?

So I got a new iPhone 5S and loaded all my information on it including iCloud but I want to sell my old iPhone so I wanna remove the iCloud off it… If I press delete account would it just delete my account from the old phone or delete it in general? And is it better if I just press erase all contents and settings?

Iphone 5s loosing Wi-Fi connection

I'm getting fed up of my iPhone 5s loosing Wi-Fi signal, it will go back to 4g or 3G or gprs it is really getting to me. All other devices and phones in house hold stay connected constantly. The iPhone has to prat about. Any fixes or ideas please.

My iphone defaults to text messages for certain people?

My iphone defaults to text messages for certain people?

Added (1). I can't get my phone to send imessages to certain people, even though we both have iphones. It doesn't even try to send as imessage, it just defaults to the green text messages. I'm getting really frustrated because I turned imessage off and then on, restarted the phone, etc. It imessages to other people, so I'm not sure why it's not working with others.

Will an iPhone 6 Plus from USA work in the UK on UK networks?

If my dad was to bring me back an iPhone 6 Plus from America (which is purchased from an Apple Store), will I have any issues using it on the 3 network in the UK? Will it just be as simple as putting my SIM card in and using it on 4G etc?
Hope you can help, thanks!