Visit these websites one by one. These websites are web based proxies. They will change your IP address and they will unblock your network filter. You will be able to login to Facebook. Try all the sites and at least one of them should work.
Don't pay for any of these websites. You can unlock Facebook for free. Please leave a comment here and also in the Squidoo page (http://www.squidoo.com/unlock-facebook) and say these sites works or not.
Copy and paste any one url and see whether you can unblock Facebook.
All the best.