My mobile has no service I live in Iran and my device is A1660 apple7 . What should I do now ??

The A1660 model was only meant for sale in the U.S, China and Japan, and as such that is the only place that model can be supported for the no Service issue. There is way to legally acquire that model in Iran.

By extension, there is no support for it in Iran.

You would need to physically transport the iPhone to one of the above countries to get support for that issue.

See here: iPhone 7 Repair Program for "No Service" Issues - Apple Support

You cannot send it. Apple will not take international shipments for service.

You need to physically travel to one of those countries to take it in for service to an Apple Store or Authorized service provider, or send it to someone you know there so they can take it in for service.