college student and I took out a loan with my grandfather as the co signer

I am a 22 year old college student and I took out a loan with my grandfather as the co signer. I went to Wright State University when I signed for the loan. I transferred to Sinclair College and I was contacted about my loan and I told them I was still in school. They asked me to get the school information to them so that my loan could be deferred. Now I atttend Hondros Nursing School and they was calling me to see if I could get the information in to them and I told my financial advisor about the situation. Now all of a suddent they are saying that the loan I have is a private loan and they do not do deferments and I have to pay the total amount back or my grandfather who is retired and on a fixed income is being threaten with a judgement against him. I was told that as long as I was in school I could defer my payments until 6 months after graduating. They are saying I could not switch schools, during at no time. I left Wright State because it was too expensive. I felt that if I was still in school and I let them know that and where I was attending why am I suppose to pay back a loan, and they want the whole 12,700.00. I need some help to know how is this possible.