Why can you not just do it right the first time? What is so difficult?

I took out a mechanical warranty plan with First For Woman insurance. When I found that the cost to service the car at a mechanic was totally unreasonable and I was able to perform the service myself I canceled the policy. I expected that there would be a months notice for the cancellation so thought nothing of it when they deducted money from my account the following month. I didn't notice after that until this month that they were still deducting money from my account. WAKE UP YOU USELESS PEOPLE. THE POLICY IS CANCELED, STOP *****ING MY MONEY