Internet fails between 11:30 and noon

For the last 3 out of 4 days, my internet has failed starting between 11;30 am and noon and stays down for a good 4 to 5 hours. Xfinity says it is my modem because they see no outages. Everything lights up on modem except the internet icon. About had it. They want to send someone out and charge me if they have to come in house.