My iPhone keeps saying "This accessory may not be supported"

My iPhone 5c kept saying "This accessory may not be supported". I knew what the problem was, I had to get a different charger. I kept putting it off and off. This morning it kept doing it and doing it , more than usual. When i was closing my apps it said it twice in about 0.2 seconds. I tried to press dismiss but it wouldn't work. I shut my phone off and tried to do it, and it wouldn't work. Now it's been about 20 minutes of me trying to press dismiss. I can't do anything with my screen or anything like that. Someone tried to all me but i couldn't slide it to answer it. I tried restarting it but, as we know, it is not letting me work the screen. it still says "This accessory may not be supported" how do I fix it??