My iphone 4s will not restore not eligible for restoring?

Im not sure what is going on.. I have bought an iphone 4s on ebay and the phone worked at first. but it keeps showing the connect to itunes picture i connect it, and it says the phone is up to date but it needs to be restored. Everytime i do it it says unable to connect to the itunes store not elgible for restoring? im not really familiar with apple i own a droid so will someone please help.