Use the asterisk (*) with the number series to block that entire series. If you want to block a series of mobile (like CUG) numbers then in the blocklist settings in your call settings, add a rule like 98865* then it will block all calls from numbers starting with 98865.
For example,
This will block all calls from numbers starting with 140.
You can also use 3rd party apps like Truecaller etc. to achieve same result.