Really poor after sales service

I had a leaking overflow pipe and was advised by Suntank to replace PRV. PRV was replaced but problem persisted and only cold water coming out of hot tap. Suntank advised of the problem to which they said that plumber had installed PRV incorrectly. Plumber was prepared to send photo of installation which was refused by Suntank. My plumber then proceeded to disconnect the solar and reconnect to my old geyser. Two weeks have passed and no joy. Suntank does not respond at all and when they did last Monday 19/10/2020 its was to say that they will charge me to send someone out because they will need to undo the old geyser reinstallation. I told them that the plumber would reconnect back to the solar as soon as I have a time but no response to now. The solar system has a 10 year warranty and has been serviced every 2 years by Suntank at a cost.