Does the employer have the right to prevent me from working in a skilled trade position. (HVAC tech)

I am a service technician for a residential HVAC company in Johnson County KS. At the time of employment I also signed a 3 year contract of employment and a no compete. As it was explained to me at that time, the no compete was valid should I terminate my employment during the 3 year contract period as well as the cost of my schooling. I have fulfilled the 3 year contract in full. I am not starting a competing company nor have I made any efforts to influence any of their clients. I am changing places of employment to an already established competitor in the Johnson County market. My current employer is threatening to enforce this no compete and prevent me from making a living.