" Sent a letter of ceasing all phone calls" Did you send that letter certified, return receipt? If not then they will claim they never received it. All written communication with a DC should be sent so that you have a way to prove they got it. The Auto dialer is not an excuse, not legally anyway. You have an excellent FDCPA and TCPA claim.
Read up on your rights here, get template letters to send and also make a complaint at this government site: http://www.consumerfinance.gov/
Also file a complaint with your State Attorney General's office.
List of State AG’s offices: http://consumerfraudreporting.org/stateattorneygenerallist.php