Blocking Country Codes

That is not a feature that Apple provides. You can tell them it's something you'd like to see here:

Product Feedback - Apple

Meanwhile, you might try some of the spam-blocking apps available in the App Store such as RoboKiller or NoMoRoBo. You might also see what your carrier has to offer. My carrier offers some basic blocking services for free and additional services for a fee. I don't know if this is one of them as it's not something I need so I've never inquired.

Please contact your Carrier for the same. Do tell us what they say.

Apple Inc says; "We read all feedback carefully, but we are unable to respond to each submission individually."

Here is how for iPhone · Country or region* Select your country or region. · Feedback Type* Select feedback type. · Comments* Enter a comment.

Feedback - iPhone - Apple