https://wccftech.com/several-pixel-3-users-on-att-experiencing-lte-connectivity-issues/

The Pixel line of phones (and even other big-name devices for that matter) are no strangers to network connectivity issues. Just recently, the Samsung Galaxy S10 ran into some trouble with Sprint users. The problem has since been fixed, but today, some Pixel 3 and Pixel 3 XL owners on AT&T are having a hard time connecting to the service provider’s LTE network.

The problem was first spotted by Android Authority. It has made the round of Reddit and AT&T forums for a few months too. According to affected users, the Pixel 3 has troubles reaching AT&T’s LTE network shortly after disconnecting from WiFi. Instead of the LTE symbol, you see a large ‘x’ indicating that LTE isn’t active, despite having strong signal strength.