missing itunes balance

hi all,

i changed my itunes email account online, and then changed it on my ipad as well, restarted the ipad deleted my apps and re dowload them with the new apple id, i looked at my itunes balance and it shows me that is $0 when i know i had $56 on it i had a $50 gift card gave to me for my bday last september and a $10 one (of which i used $6) and now they are gone... how do i recover that?

thanks for your help