Hi there,
First thing to check is your APN settings. Make sure that they match your carrier. If they do match your carrier, try deleting the APN for your carrier and recreating it manually. This can often help.
If APN settings do not help, then certainly update your baseband. It should not brick your device, but your question makes me think you should read up a bit more on what you are wanting to do. Just to make sure you understand the process.