How to hack through a password on at&t phone?

so, my friend has an at&t phone, and its a straighttalk phone from walmart. We forgot the code and was wondering if there was any way we could get by and go change it to something we do know. We've tried everything but cant figure it out? help. btw it looks likes a blackberry.and there is no "i forgot my password" button" or "sign into gmail if you forgot your password" it just says "enter code" and has four dashes. Is there anyway we can get it without having to call at&t or going there.