My iphone xs max is carrier lock how to unlock my phone

Only your carrier can help you with unlocking your iPhone. Contact your carrier company!

How to unlock your iPhone for use with a different carrier - Apple Support

You are going to have to find out what carrier the iPhone is locked to. If you bought the iPhone new, you should know. If you purchased it used, then ask the person you purchased it from. Otherwise, you can contact Apple Support and ask them. They will need the serial number of the device.