Q: block stolen iphone

Ask your carrier if they can blacklist the IMEI.

If you enabled Find my iPhone, you can go to http://icloud.com and remote lock it.

If the thief restored it, they will not be able to reactivate it due to Activation Lock: http://support.apple.com/kb/HT5818.

My iphone 6 was stolen, how do I block it?

You contact your carrier and ask if they provide blocking services. Only the carrier can block the phone, you cannot block it yourself. Read stevejobsfan0123's response for additional information.

Thank you, I will do.

You're welcome.