create a android service to check for the incoming call into the blocked list numbers and if the number wont get matched then let the caller speak with the calle

consider there are a list of junk callers who call us daily and irritate [login to view URL] i need an android service where in if any junk caller calls in then before our cell gets ringed the service should check for the junk callers number into the block list [login to view URL] the number is not present into the block list then the caller should be let to speak with [login to view URL] if the number matches in the block list then perform this task: ->generate a random audio captcha numbers. ->match the junk callers numbers with the captcha auto generated. ->if the junk callers captcha matches with the auto generated captcha then let the junk caller communicate with the user that is me else terminate without notifing to the user..