White Apple IPhone 3g or 3gs *

Hi The phone is screen is in good condition and the back is in used condition the phone was working perfectly then all of a sudden i got an apple logo sign coming up when i put it in the charge the phone for you do not now what is the problem but if you do then this is . i was using it on t-mobile but may be unlocked. i am going to buy a new phone so i need the money. cash on collection. Sorry i cant tell difference between 3g and 3gs was given to me. thanks