Telgea's Voice/Text/Data plans typically come with 5G connectivity. If you have a "Device Plan" that is data only, it may be limited to 4G.
If your 5G-enabled plan is only making a 4G connection, the troubleshooting steps are as follows:
Ensure 5G is enabled on your phone
iPhone: Go to Settings > Cellular > Cellular Data Options or Settings > Mobile Data > Mobile Data Options
Android: Go to Settings > Connections > Mobile Networks > Network Mode
Try turning Airplane Mode on and off on your phone, to allow it to reset it's connection to the network.
In some cases, a full restart of your phone may be necessary.
If there is still no 5G connectivity, please reset your network settings
iPhone: Go to Settings > General > Transfer or Reset [Device] > Reset > Reset Network Settings
Android: Settings > System > (Advanced) > Reset options > Reset network settings
If all else fails, please contact support and inform them of what device you have, to receive the network settings to be manually entered and instructions on how to do so.