I add to delite a gig that was in 5 gigs order, but i cant see the credit of it.

Hey to all in the Forum, i had a problem eith a seller, he took far of what i was expecting, i ad to had some 3 more gigs after the first 2 but now i see is only a 5$ in my account and i don't know how to use it.
Can any one kindly help me?