My children disabled my iphone 3g, it reads "iphone is disabled connect to itunes" what do I do?

I have a iphone 3gs, my children where trying to get on to my phone and they where putting in the the wrong password so my phone disabled. I called up apple and they wanted to charge me $20 to unlock it. I have already paid enough money for this phone, I only use my phone to play apps it doesn't have phone service. I just use the wifi, so if anyone can please help me it would greatly appreciated , thank you. oh my phone is saying iphone disabled connect to itunes, I don't have the charger to connect it to the computer.

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