MiWay Car Insurance failing me by refusing to payout for my car insurance

I was recently in a car accident. Well I drove into a car as I was making a turn, unfortunately I did not see it there. I pay my insurance on the 25 and I missed my payment and called MiWay to make an arrangement prior the accident had occurred and we had an agreement of the new deduction date which would be now the 15th of each month. When the accident occurred, a case was opened and I sent everything which was required to MiWay to make a claim. To my understanding, one is given a 15 days grace and I was well in with in my period of grace when the accident occurred. Today I received a call that my claim not a success, when I ask why I’m told of the missed payment and that I was not in grace. In such a situation what does one do. I’ve got all the evidence needed for the communication which I had made with MiWay. I’m frustrated because I’m failing to understand this poor excuse.