Hi
I apologize that you're having issues logging into the current GoPhone website to manage your account.
GoPhone online accounts are in the process of migrating to use myAT&T, which is the same website that our regular post-paid customers use and will give you even more control and detail of your account. myAT&T for GoPhone launches on 7/25/2014 at which time you'll be able to register at att.com/myatt
In the meantime if you need access online you can visit an AT&T Company store and they can reset your PIN for you in store with presenting valid Photo ID. Customer Care over the phone may be able to reset it as well, but usually will need have your old PIN to reset to a new PIN.
You can find your nearest AT&T Company store by clicking Here
Hope this helps!