If you receive a lot of spam calls from a specific area code and prefix, you have the ability to block that. In the Mr. Number Android app, click on the Block List tab. Click on the + symbol at the bottom right and you should be able to choose the option to block "Numbers that begin with." You can then input any area code and/or prefix that you might be having issues with.
Please be aware that the block option might block all calls with the area code or area code and prefix. Even those in your contact list. This is something that we hope to fix in a future release. Meanwhile, this is working properly in our our newer app, Hiya, if this is an issue for you.
You can download Hiya here: https://hiya.com/downloads