My brother used to be a student of BITS Pilani and from what he has heard; it is not a good institute for students who want to pursue pharmacy.
You should pursue pharmacy at BITS Pilani only if you have a strong background in physics, chemistry, and biology or you cannot get admission to some other institute.
Even if you do have a strong background in the three subjects, the chances of getting converted to a different stream are very low. You have to obtain a CGPA of or higher than 9.8. It is simply too high and getting a 257 just will not be enough.
On the other hand, BITS is a very reputed institute. It is highly praised by my friend and a lot of the students and former students as well. It is a very good institute but pharmacy is just not its forte. It would be better if you look for other institutes if you want to pursue pharmacy.