Calls from these jerks come at least once a day.....telling me it's my "last chance" to lower credit card rates. If these morons came knocking at the door every day, they could be arrested for trespassing and/or harassment. Why can they get away with doing it by phone???

You should call your local police. This is the procedure for these types of calls. They document your info and pass it on to the FCC.
You could file directly with the FCC.GOV  just write down all the different numbers they call from and file one big claim. When they catch these people as they have in the past you would be entitled upto $75.00 per call. So make sure you sign up on the DO NOT CALL LIST AT THE FCC OR YOUR PHONE CARRIER FIRST.
Good luck. It works

7/7/15 4.21pm

https://www.donotcall.gov/register/reg.aspx

here is the web site to sign up for the do not call list

https://www.donotcall.gov/register/reg.aspx

here is the web site to sign up for the do not call list

https://www.donotcall.gov/register/reg.aspx

here is the web site to sign up for the do not call list