There are some good Water Conditioning Specialists, Plumbers and Well Pump Contractors out there who sell and service water conditioning products but you will need to find them. A quality contractor would likely be accredited and in good standing with the local Better Business Bureau so start there. Google WATER CONDITIONING PROFESSIONALS NEAR ME, or PLUMBERS NEAR ME or WELL PUMP CONTRACTORS NEAR ME. Look at their Google reviews if they have a web presence or website.
Get an estimate over the phone asking what their normal service call rates are. If they will not give you their hourly rates over the phone, call someone else. Tell them what type of system and series of control valve that you have and ask if they have parts and expertise on your system. If they do not service systems other than what they sell then call someone else.