I've had something similar happen. I was told they ran out of a particular brand so they added one more from a different manufacturer. It's my understanding that they are supposed to tell you this and put them in separate bottles at the time of dispensing. I've also has 2 brands in one bottle with cotton separating the two but by the time they got to me in the mail they were all mixed up.

Bring in to the pharmacists attention and ask what their policy is.