My iphone got locked

First, by "locked" do you mean disabled? There are multiple types of locking on a mobile device but disabled means something else. Click on the links below to find instructions on how to deal with your specific situation:

1) iCloud: Activation Lock - https://support.apple.com/HT201365 - This is a security feature so only legitimate (i.e., not stolen) redistribution of devices is possible. See: 'How to remove Activation Lock' --> https://support.apple.com/HT201441 - If an activation lock was put on a device, only the owner of the account that applied the lock can remove it. Get them to remove it or return the item for a refund. If you are the owner, see the part at the end about asking Apple to reset the device.

2) Carrier lock: Read this link on "How to unlock your iPhone for use with a different carrier" -

http://support.apple.com/HT201328

- Only some carriers offer the ability to unlock iPhone for use on any carrier. Follow the instructions in this article to unlock your iPhone.

3) If you have a forgotten/unknown device passcode, or have a disabled device, unfortunately you have no option but to erase the device. However, you can eventually restore the data and settings from a backup you made before the device was disabled. You must have a computer to use the method below. If you don't have a computer, borrow one from a friend, or go to an Apple Retail Store or Apple Authorized Service Provider. You can also use a PC with iTunes. You will likely also need your Apple ID and password. All Apple mobile devices follow the same general procedure but the link below and other links off it provide model-specific instructions:

If you forgot the passcode on your iPhone, or your iPhone is disabled", click here --> http://support.apple.com/HT204306

Here is a related video which to me has more complete and clearer instructions: https://www.youtube.com/watch?v=7s8-zLG9ySQ

Steps:

1. With the device disconnected from a computer use the model-specific instructions in the links above to shut down the device.

2. Connect it to a computer with Finder or iTunes (Mojave or earlier, or PC).

3. Restart into recovery mode (black screen with a cable indicating attach to computer).

4. When prompted, click "Restore" to erase data & settings, and update system software. May take some time.

5. Set up your device ( https://support.apple.com/kb/HT202033 ). Partway through you are offered the opportunity to restore your data and settings from a backup, or you can do this at a later stage ( https://support.apple.com/HT204184 ). Even if you have no backup, if you were using some iCloud services to sync items such as Contacts or Photos those may reappear once you sign back into your iCloud account --> Set up iCloud on your iPhone, iPad, or iPod touch - https://support.apple.com/HT208681

'If your computer doesn't recognize your iPhone, iPad, or iPod' click here --> https://support.apple.com/HT204095

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On the contingency you are asked for your Apple ID and password AND you have forgotten those:

If you forgot your Apple ID, click here --> https://support.apple.com/HT201354 ; your Apple ID password, click here --> https://support.apple.com/HT201487 , or to jump directly to the forgotten sign-in information help site, click here --> http://iforgot.apple.com/

What to do after [or before] you change your Apple ID email address or password - https://support.apple.com/HT204071

If you still need help, contact Apple for help with Apple ID account security --> https://support.apple.com/HT204169

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As for iTunes versions, what you need depends upon the computer model and system version it runs. Apple stopped using iTunes several years ago on Macs. You use Finder instead. It is still used on PCs. Update to the latest version of iTunes - https://support.apple.com/HT201352