Q: how i can update if my iphone havent got software update

Vital Resources For Your iDevice (Updating, Apple ID, and iCloud)

A. Upgrading iOS

   1. How to update your iPhone, iPad, or iPod Touch

   2. iPhone Support

   3. iPod Touch Support

   4. iPad Support

     a. Updating Your iOS to Version 6.0.x from iOS 5

          Tap Settings > General > Software Update

     If an update is available there will be an active Update button. If you are current,

     then you will see a gray screen with a message saying your are up to date.

     b. If you are still using iOS 4 — Updating your device to iOS 5 or later.

     c. Resolving update problems

        1. iOS - Unable to update or restore

        2. iOS- Resolving update and restore alert messages

B. Apple ID Support

   1. Apple ID FAQ

   2. Find your Apple ID

   3. Recover your password

   3. Change your Apple ID

   4. Change your password

C. iCloud Support

   1. What is iCloud?

   2. How to set up iCloud

   3. iCloud: System requirements

   4. Using your Apple ID for Apple services

   5. How to back up iCloud data

D. List of iOS Devices and What They Support

   1. Identifying iPod models

   2. Identifying iPhone models

   3. Identifying iPhone models

E. User Manuals

   1. iPads

   2. iPhones

   3. iPod Touches

but the software update choice is not written in general ..