Mixing medications with insulin

My father in law was prescribed insulin, then doctor cancelled that, and then prescribed Actos. (He is 92 yr old and has managed diabetes with pills thus far.) Supposedly the doctor cancelled the call in prescription for insulin and later called in the prescription for Actos. When FIL went to pharmacy to pick up the Actos, they had stapled to it the insulin and he paid for both not realizing what he was buying. The pharmacy refuses to give him his money back for the insulin. Does he have any recourse? Could it be dangerous mixing all his oral diabetes meds, plus Actos AND insulin? Shouldn't the pharmacist have caught this? We are upset because he is having a hard time paying for all his meds as is....  Could someone advise if he has any recourse with the pharmacy? thank you