Robo No More is a very simple app that blocks all numbers similar to yours (with the exception of anyone in your contacts).

For example, if your phone number is (212) 867-5309 and you keep getting phone calls from numbers like (212) 867-2938 or (212) 867-8392, then Robo No More will prevent all spam callers from reaching you.

This will not block all spam calls, only the spam calls that have been mimicking your own phone number.