This app monitors the incoming calls. When the phone number starts with specific digits, it hangs up the call.

Frequently getting telemarketing calls? Input the number of the call center to get it blocked.

A number prefix can also be set to pass through the filter. You may apply this to your corporate office numbers.

The app keeps a call log and you may edit the filter prefixes from there. It helps taking the guesswork out of number prefix input.

How about the numbers in your contact list? They are not blocked by default. So normal calls are not affected.

Travel to a foreign country where the incoming calls have format changed? You may disable the filter for a while.

The filter prefixes can be exported to a CSV file. You may edit the CSV file in your PC and the app can import the modified file.

This app is free of charge. No ads. Give it a try!

Feature summary:
✓ Blacklist
⇒ Specific prefixes that are blocked from the user.
✓ Whitelist
⇒ Specific prefixes that are allowed through the filter.
✓ Exact number
⇒ The prefix can be specified an exact number.
✓ Number length
⇒ Setting to allow through numbers of only certain lengths.
✓ Contacts
⇒ The number in contact list is allowed through the filter by default. This feature can be disabled.
✓ Unknown number
⇒ Block an incoming call which number is not shown. This feature is disabled by default.
✓ Disable filter
⇒ The call filter can be disabled.
✓ Call log
⇒ The app has a call log page. The context menu features filter editing and web search.
✓ CSV export & import
⇒ The filter rules can be saved to CSV file for backup and transfer purposes.

Get started with the user manual in the web site.
http://sites.google.com/view/callprefixfilter/home/user-manual

Some examples are given to illustrate how the filter works.
https://sites.google.com/view/callprefixfilter/home/user-manual/how-it-works