Boiler Pro Heating & Air Conditioner

Phoned Boiler Pro because of fluctuating pressure in my boiler system: too high (30+ psi) with water being released from PR valve, and too low (5 psi) when the system is cooling. I was grateful that a repairman would be sent the next day, but the repairman was a sub-contractor from another company. I was informed when I phoned that the diagnostic visit would cost $180, and that the repair would be made if feasible. The visit lasted maybe 20 minutes with nothing being done except tapping on the expansion tank and lowering the pressure by releasing water via the PR valve.One year ago, the PR valve, expansion tank, and filling valve had been replaced (the original installer could not come out because of COVID-19 in his family). I was now told that the filling valve was likely not working, but he didn't have one with him, so he couldn't make the repair, saying that Boiler Pro would contact me to replace the valve. He charged $180 + tax and failed to give me an invoice/receipt (I only realized this later when I was trying to figure out what the company's name was).I question whether the filling valve indeed is the culprit, since when I turned the water off that enters the system and lowered the pressure by draining some water out of a radiator, the pressure still increases to 30 psi opening up the PR valve to release water again. Also, it has been 5 days, and I have not heard anything from Boiler Pro.