Sounds a bit like homework...
Break the project down.
Step 1: Making the calls.
Are you going to use a USB modem, or serial? Have you got the code required to talk to the modem and make calls?
Step 2: The response.
You'll need to be able to pull the sound from the call from the modem, and record it. Then you'll need to have the program decode the sound and pick up the frequency of the tone, and determine if 1 or 2 was pressed (or if the person hung up).
Step 3: Sorting the results.
This part can be as simple as making a system call to append text to a file that you can read later (or you can write the code to open the file in append mode, seek to the end, and write the information there).
Step 4: Reading a list of numbers to call.
This one is trivial, since it's one of the first things people learn when they learn how to program.
Step 5: Automation.
Depending on how you want it to run, you could set up a cron job to trigger a script to make one call every minute (unless one is currently in progress), or you could just have the program run with a loop, making as many calls as possible.
Steps 1 and 2 are the big ones. If you can't pull them off on their own, the rest of the project isn't going to be worth building.