there are 4 method to unblock ur airtel sim:
=>Method 1:-Just send MSG for porting in back call says i purchased an airtel sim for free FACEBOOK many user's using airtel free facebook in mobile and pc.But in my sim not facilities available right now so i am porting.after 2-3 hours your site automatically activate.
=>Method 2:- First you deactivate your airtel 3g on any GPRS randomly.then remove them 4 days and keep your sim in safe area. Now use another sim on your mobile(this is the main trick). Now insert your old sim after 4 days and now again your sim activated.this method safe and secure.
=>Method 3:- Best method forever create MSG "FACEBOOK" and send to 54321.send MSG above continuously at least 10 times. Now after this work restart your phone and get successfully active sim unblocked.
=>Method 4:- First remove your sim from your mobile and again put sim in GPRS unable handset phone like 1100,1110,nokia 1600. Now send MSG "MO" to 54321.Remove and put sim in GPRS enable mobile phone (in this required time minimun 5 minutes between remove and put sim in GPRS Enable handsen.
ALL DONE.
Here are some tricks to unblocked ur blocked airtel sim-: