Generally, no. However, it is always recommended to back up your phone before altering system settings. Will the unlock be permanent?
Some "free" servers eventually demand a "membership fee" or require the user to download suspicious "verification" apps (adware) to complete the process. free unlock server verified
To help me provide more specific steps or guide you to the right platform, tell me: What is the of your phone? Which network carrier is the device currently locked to? Generally, no