This happened to us twice also, so your not alone. In our case our script goes straight to the chemist, so i never actually see whats on it, first time chemist handed me a bag with humalog 50, then second time the same. The starting point of the problem was actually the receptionist at the clinic, when i nicely told her of the mistake the first time she apologised and said she'd rectify it. Second time i wasn't as nice and she's altered his medication on his records and i got a print out to double check it. Appartently both had been added to his records and when asked for a repeat prescription, instead of looking for Humalog, they print off the first Humalog they see, which was Humalog 50, (which funnily enough my son had never been prescribed in the first place!!!)
Sorry long post, but your problem could be generating from the same point, as chemists are normally so thorough in dealing out drugs.
Suzi x