Safecart.com Lower than whale stuff. When their service refused they locked up my machine-now no refund. Internet

I purchased a speed boost from Safecart for nearly $30 and before it wasw installed good, a salesman tried to talk me into a $295 on line overhaul which I refused.

The salesman had been inside my computer pointing out supposed problems and when i refused to reconsider the purchase, he said "okay, I'll exit your computer".  He did that but when he left, he left a little present, a totally locked up computer.  He immediately hung up the phone.

I called the company back at 1-855-966-5665 and told them that i wanted a refund because I had made a mistake in purchasing their services because I was not smart enough on computers to use them. 

They said they would send me an email describing how to file for a refund but they have not sone so.  Being a retired law enforcement officer I should have known better but advancing age has taken the edge off my thought processing.  These people are evil and it has cost me a computer doctor visit to get it going again.

Please help me with this problem.