Non payment of repairs done by the plumber

I phoned the call centre and informed them that I noticed that my geyser was overflowing. When the appointed plumber came through, he informed me that the cover I have does not cover for the safety valve and thermostat. I phoned again yesterday and left a message for the consultant that was assisting me and I had nothing from them. I have been paying this policy for over 8 years and now I when I am making a legitimate claim they tell me that they cannot assist me. Every month they deduct my money and now they don't want to pay. I am sick and tired of business that hide behind so called Terms and Conditions.