hi, I want to lock my stolen IPhone using IMEI NO. how can I do that?

You can't use the 'Find My iPhone' facilities with the IMEI number - you have to have set 'Find My Phone' set up on the device before losing it. If you ring your Service Provider they may be able to lock it. AFAIK this lock is permanent and cannot be undone.

You cannot lock it if you have not enabled find my phone. All possible solution in case your iPhone is stolen here: If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Info from support article:

If Find My iPhone isn't enabled on your missing device

If you didn't turn on Find My iPhone before your device was lost or stolen, you can't use it to locate your device. However, you can use these steps to help protect your data:

1. Change your Apple ID password. By changing your Apple ID password you can prevent anyone from accessing your iCloud data or using other services (such as iMessage or iTunes) from your missing device.
2. Change the passwords for other internet accounts on your device. This could include email accounts, Facebook, or Twitter.
3. Report your lost or stolen device to local law enforcement. Law enforcement might request the serial number of your device. Find your serial number:
   • On the original box or receipt
   • On My Support Profile (supportprofile.apple.com) if you registered your device with your Apple ID
4. Report your lost or stolen device to your wireless carrier. Your carrier can disable the account, preventing phone calls, texts, and data use.

Find My iPhone is the only way that you can track or locate a lost or missing device. If Find My iPhone isn't enabled on your device before it goes missing, there is no other Apple service that can find, track, or otherwise flag your device for you.

i want to lock my imei number

If you read the thread, you cannot do it. Only your cellular carrier can block your IMEI. Contact them.

As was stated over a year ago, you can't do that. Please read the responses in the thread you're replying to before adding a "me too".

in some countries when you report the phone stolen to the police you can give them the IMEI number and they have all carriers in the country block the IMEI from working on networks

at any rate it's not an apple thing it would not be legal for them to do anything

not be legal for them to do anything

How to reach carriers

paco__kiatu wrote:

How to reach carriers

Your carrier is the company that you pay for your cellular access.