credit card tuition

I enrolled in the plan to pay tuition on a credit card can I change my payment method
I enrolled in the plan Payment of Sallie Mae to cover my tuiton but I used a credit card as payment for my day, I asked myself that I can change a current account, he said I could pay by electronic check, but I can not afford after paying by credit card for 2 months
Convinced that should be able to change it, but give them enough time to change before your next payment.
U of Calgary protest not accepting credit cards for tuition