Internet (Ethernet and WiFi) cuts out every 15 minutes.

Please start here if you wish;

https://forums.xfinity.com/conversations/your-home-network/connection-troubleshooting-tips/602da777c5375f08cdea3db9 

Day 2 of no internet  

This is frustrating.  I can’t even call a Comcast store and ask for an exchange on the modem they rent to me.  I checked all connections.  

Wait for your appointment.  

Hello @user_xvbdkc, thanks for taking the time to reach out on our Forums! We value you as a customer, and I am sorry to hear about the connection issues you've been experiencing. I definitely know how important it is to have a working and solid connection, so I hate to know that you've been having this problem. My team is here to help! 

Please know you can always swap your modem out for free at an Xfinity Store location. Follow this link https://www.xfinity.com/local/store-offers, to find a location near you. 

My team would love to follow up on your appointment and provide any other support needed. Please send us a Direct Message so that we can better assist you. Here are the detailed steps to direct message us: 
 • Click "Sign In" if necessary
 • Click the "Direct Message icon” (upper right corner of this page)
 • Click the "New message" (pencil and paper) icon
 • Type "Xfinity Support" in the To line and select "Xfinity Support" from the drop-down list
 • Type your message in the text area near the bottom of the window
 • Press Enter to send your message