Is it illegal for the property to cut off commercial electricity privately?

It can't reach the legal temperature, depending on which room it is. There are clear rules: bedrooms and other main rooms. The property only charges heating fees and has no right to cut off electricity. You can find a property or heating company to respond that the temperature is not enough, and they will send someone to repair it.

When one's rights and interests are damaged, keep videos, pictures and other evidence and physical evidence, and call the police for help. If the purpose of negotiation cannot be reached, the parties concerned shall be investigated according to law, and the other party shall be investigated for responsibility and demand compensation for losses.