payment methods & family sharing

a while back i had joined my friends family sharing plan. i was having no problems until recently. today i tried to make a $1 in-app purchase with the itunes balance i had remaining. i have around $3 remaining. but every time i try and make that purchase it tells me i need to "verify a payment method" the card that is present is not mine, so i cannot verify it. is there any way i can get around this so i can use my itunes balance? i do not want to use my friends money for this so i dont want to verify his card if the money will be taken off of it. it also will not allow me to edit and remove the payment method. even if i log into the appleid website and change it from there, it will automatically go back to having that card as a payment method.