How did they gain access to your house to tamper with your thermostat? If they installed wires in the house, disconnect them. If they put some type of controller on your outside air conditioning unit, bypass it. I don't know what the laws are in your jurisdiction, but there are limits in most places as to where a utility can gain access. In general, they can access THEIR equipment, and can obtain access to yours only for reasons of public safety (for example, if you had a generator miswired and feeding into a line on which they wanted to work).
I got a job offer in Maryland that I couldn’t resist, so I left my house in Virginia and rented an apartment in Maryland. The rental office gave us no choice.