Refused to pay service

I have a 3 year service plan with 360 plus.i booked my car in today for its last service on the plan.they have refused to pay for my service.i phoned in january to ask when is the latest that i can service my car this year as it is my last.they said as long as its before october.because it expires in october.now they are refusing to pay for my service and its the 12th of september.im am extremely unhappy with there service