How to remove my plan off an iPhone?

I recently upgraded to the new iPhone and gave my friend my old one (iPhone 4.) How do I remove my plan and everything from it so it doesn't have my number or anything on it and he can just use it for imessage, email etc?

How to fix my headphone jack on iPhone?

I got the iPhone 5c literally 2 weeks ago, if that. When sound is played through the speaker it sounds great, but right when I put my headphones in its full of static and sounds horrible. This is incredibly frustrating since I just got this phone. Please help!

Added (1). Just thought I should mentioned that I tried multiple headphones, so it's definitely the phone that is the issue.

How to back up my text messages from my iphone?

I have the Iphone4 with the ios7 update. I just want to put my text messages onto my PC. I have already backed up my phone onto my computer through iTunes and I have also found the files that contain the texts. I just need to know how to read them.

Why is iOS 7 way too glitchy? When iOS 7.1 come out?

Since i updated my iPad 3 and my iPhone 4 to iOS 7 My iPad and iPhone has been glitching too much and it is too annoying sometimes my iPad and my iPhone crashes then the apple logo shows up unexpectedly and my iPad and iPhone lags at times. When apple release iOS 7.1?

Added (1). Btw all my apps are update for the iOS 7

Added (2). All my apps except for few (like whatsapp) are optimise for ios 7

I look ugly in my iPhone 4S camera, but fairly nice in the mirror?

So, as the title says, I appear way different on camera than I do in any mirror. My phone is almost a year old and the camera has not been damaged, yet sometimes I look hideous in the camera. Mind you, I'm self conscious, but there's a noticeable difference between the two. I wanted to know two things: Do people see me as the mirror image or the camera image? And why does the phone camera appear different than the mirror?

My iphone lags when I watch youtube, skips couple seconds while i listen to music?

Ok so I don't know why but since I got the new ios 7 update, my iphone started to play funny. The other day I was playing music and I noticed that it was skipping seconds in a song in like 1/5 songs. Today on netflix and youtube, my phone starts to lag when I open either youtube or netflix. Like the video needs time so it goes back to normal. I don't know if it's the update that I should be worried about or my iphone. Btw it's an iphone 4.

When will my iPhone 5s be here?

Before I get hate by android users, I have had 4 android phones, I have an iPod and I'm just looking for a different phone. I ordered my 16 gig Gold iPhone 5s from Verizon on September 28th and they told me at the store that i should expect it any time in October and that some people have even gotten theirs within a week of ordering it. I just want to know when i should have it!