Walgreens review: ripped off on prescription 1

I noticed that Walgreens gave my mother a 30 day supply of Metoprolol ER Succinate 500 mg tablets, but charged her for a 90 day supply. The vial, which the pills were in couldn't possibly hold 90 tablets. When I showed the vial to the pharmacist, he actually tried fitting 90 tablets in it, but it was impossible. He basically told me that he'd look into the matter and blew me off. Since they charged my mother's insurance company for another 90 day supply, I'm going to file a complaint on her behalf with the State of New Jersey on the matter. I realize that people are human and make mistakes. However, since a national company like Walgreens fills people's prescriptions, they should have some kind of system implemented in place to avoid errors like this, but either they don't or their method of quality control filling prescriptions isn't up to snuff. If something like can happen, I'm wondering how many elderly people they rip off or kill a year with such incompetence.