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What is preventing you from doing so?

GB

First, we are fellow users and not Apple employees so publishing a serial number or IMEI number is a bad idea.

Do you want your iPhone disabled in some way? If so, you have to do that yourself, Apple cannot assist with doing that.

If your iPhone is stolen or lost you can disable it if you turned on Settings > iCloud > Find My Phone and then login to your iCloud account, click Find My Phone, select the iPhone and send a disable or erase signal to it.

OK, that is an entirely different question...you will need to restore from recovery mode using the instructions in http://support.apple.com/kb/HT1212

Forgotten Passcode or device disabled after entering wrong passcode

If you have Find My iPhone enabled, you can use Remote Wipe to erase the contents of your device. If you have been using iCloud to back up, you may be able to restore the most recent backup to reset the passcode after the device has been erased.

Alternatively, place the device in recovery mode and restore it to erase the device:

1. Disconnect the USB cable from the device, but leave the other end of the cable connected to your computer's USB port.
2. Turn off the device: Press and hold the Sleep/Wake button for a few seconds until the red slider appears, then slide the slider. Wait for the device to shut down.
3. While pressing and holding the Home button, reconnect the USB cable to the device. The device should turn on.
4. Continue holding the Home button until you see the Connect to iTunes screen.
5. iTunes will alert you that it has detected a device in recovery mode. Click OK, and then restore the device.

Well, then you want to re-enable it, not disable it, I presume? Here is a link with the instructions:

http://support.apple.com/kb/HT1212

Follow the instructions that best apply to your situation.

Cheers,

GB