How do I get a permanent free virtual mobile number?

You can get permanent free number from many places, but they all have some conditions. Here is complete details

1. Google Voice give you free number if you have already US mobile number. That is completely free with calling and SMS but it require you should already have US number
2. USA Virtual Number, Virtual Phone Number This site give you UK free number, but require you to receive at least one call in 15 days, this seem quit free but honestly this type of number are subscribed, so when someone call you there are more charges than normal phone/mobile call of UK

So in my opinion instead of having free number, you can try cheap number but paid one as it would cost you 2–5 $ but that would more good and valuable with panel and sms etc. I have mine one from http://virtualphoneline.com but you can get it from many places.