allied digital services, allied digital solutions charged $1705 to clean computer, and blocked my computer usage with popup. Murfreesboro Tennessee

Allied services blocked my computer using a microsoft looking popup.  I could not delete it or get rid of it without calling this company at 1-888-663-9346.  Their announcement said my computer would crash if I did not call back in five minutes.  Their warning speech went on for over an hour. The wanted to charge me up to $700 dollars for lifetime coverage, plus acleanup charge of $199, plus $300 for a disk to clean up my computer.  After all charges it totaled up to over $1700.  They wanted me to write out a check copy it, and mail it immediately. They have called on my home phone and cell phone every five minutes for over twelve hours.  How can I stop them?