my iphone was stolen today and i want to lock it and i have my serial of my phone

See below.

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

You can login to your iCloud account at www.icloud.com and lock it from there. Other than find my iPhone and iCloud, there is no other means to lock a device remotely. Your serial number has nothing to do with it either.

You can report it to your carrier to see about getting it blacklisted.

Also, fyi, these are volunteer user community forums. Expecting an answer within a minute of posting is extremely unrealistic. If you need immediate support, then contact Apple support.

In the following support guide you'll find all what you can do:

If your iPhone, iPad, or iPod touch is lost or stolen - Apple Support

Regards and best of luck

Giulio

Oops, Stedman, I didn't see your reply in time. Please forgive my intrusion, 'cause I didn't add anything more helpful.

Giulio

Never a problem 🙂. It reinforces my advice to the OP.

🙂