To fix incorrect APN settings on your T-Mobile device, follow these steps:
Go to the device's settings
Select the "Mobile Networks" or "Network & Internet" option
Tap on "Access Point Names" or "APN"
If there are multiple APNs, delete all of them
Tap on the "Add" or "+" button to create a new APN
Enter the correct T-Mobile APN settings provided by the carrier
Save the APN settings and restart your device.