Switching Services on iPhone 5s?

I would like to get the iPhone 5s, but my contract is going to run out in a few months. I currently have service with AT&T and when it runs out, I'm going to switch over to another carrier. If I get an iPhone 5s with AT&T, can I switch it over to another carrier, or would I have to get a completely new phone.

What is bill me later? How does this work?

I wanna buy an iPhone 5 and this blue thing popped up saying BillMeLater but how do you use it? How does this work? Also I'm at this website called Rakuten.com cause I wanna get an unlocked iPhone 5 since I can't find another website who is selling them.

Added (1). I forgot it says '"Yes, I'd like No Payments for 6 Months on orders over $250!'' so help? Ten Points!

When will I get my iPhone 5s?

Yesterday, I ordered the iPhone 5s. I checked the order status and it said they will ship it from October 1st to October 30th. I don't know if this is true or not. There are two items on the order status page; the phone and the SIM card. It says the phone is preparing to ship but the SIM card is on back order. Does this mean my phone is in stock? How long will it take for the SIM card to be in stock again and for my phone to ship?

Iphone help? I have to pay for free apps?

So I have the 4s and I haven't payed the bill for it for 2 months so I can't call or text. Now when I want to download apps, it says I have to pay for them? Even for free apps! Is this normal? If not can you tell me what I can do to fix it or why it does it?

How long does the iOS7 update take?

I have a iPhone 4 and am debating wether or not to update to the iOS7 I have heard and read mixed reveiws about it.
So my questions are
•what is your opinion on it
•how long does it take
•should my phone be fully charged beiges or will it charge while its doing it
•what does it change and is it for the better or the worse

IPhone 5s versus Samsung Galaxy S4?

I currently have the 4s and like it, but want a new phone. I was thinking about getting 5s but I also am thinking about s4. What ones the better phone to get? I don't like the way memory works with apple and I know people who say the s4 gets better battery, but that could change… So what do you think is the better choice?

Why did my ios 7 update not work?

It wouldn't download at first then it downloaded. Then it wouldn't install. Finally acted like it was installing, it reset my phone then when it turns on it didn't do anything. Acted like I didn't even download at all. Why? I have iphone 4