MASTERCARE - NO CARE AT ALL

I have been having numerous issues with service from Mastercare and the company they use to have the repairs done. My lastest problem is that they have taken my oven to be fixed on the 6 March - I get a call today saying they cannot get the wiring diagram needed to fix it and will return the oven to me and remove it off my contract. My question is this - what happens to all the premiums i have paid to cover that appliance - so - is it acceptable that they cannot fix the oven and now just return it unfixed and remove it of the contract. So - this "service" that they offer is not really to fix appliances - its to get money of us and return the appliance after having taken all my premiums. I have had the worst service from them - they have no idea what customer service means or what it means to give feedback to a client. Having been with them for over 20 years - i have to say - the quality of their service has dropped drastically. its really no service at all.