You have a lot of options here. If you want to find the solution that will meet most peoples' needs, you should consider real-world scenarios. How are phone numbers related? It's pretty rare that there's any real relationship (that a customer would want to filter against) between multiple DIDs that share the same digits in the 7-10th digits in the 10-digit number. The only thoughts that come to mind are Papa John's pizza places--they seem to ask the incumbent telcos for NPA-NXX-7272 (PAPA) or some other repeating pattern, and there's no guarantee that they get it)--or that businesses often seek numbers like this: (NPA-NXX-x000). However, there's nothing to say that residences are never assigned "x000" numbers; in fact, I know of at least one without thinking very hard.

The watch-out I'm presenting here is that if you make the filtering 'too powerful' you may well run into the law of unintended consequences. Your system will end up blocking the calls your customers program it to block, rather than the calls your customers intend it to block.

For domestic pattern matching, you might be best served with a system that only uses numerals and 'X' characters that match digit-for-digit (as opposed one or more times). That way, all patterns the user enters must be ten digits long (nice error check), and it should be pretty explicit. Customer can choose any of the patterns:
919XXXXXXX (block all 919 area-code calls)
XXX249XXXX (block all calls from/to 'exchange' 249, no matter the area code)
XXXXXXX249 (block all calls ending in 249, though I'm not sure why)

You could have a radio button to select domestic or international call pattern matching, where the domestic calls have the ten-digit requirement and X or numeral limitations. For international calls, though, having a wild card that matches one or more digits would be necessary. There again, most people would be blocking calls to/from a specific country (or part of a country); I would expect most blocking patterns to specify the beginning of the pattern specifically, followed by a variable number of digits (e.g. 01144* to block all calls from country code 44 vs 011*44 for any international call with "44" in it).