We have this problem frequently. I find that persistence is the key. Also much over a phone call I prefer the portal or email or any written and traceable method of communication.
Also, a friend who’s a doctor gave me some advice when I was struggling with health issues and medical incompetence recently: be polite and persistent and KEEP IT SHORT. (Last one, not a core competency of mine 
)
The doctor/staff/whatever doesn’t have the thru put to care about your backstory. Even if they want to. They have hundreds of patients to help. So get right to the point. In your case that might sound like “I am a patient of Dr. SoAndSo. I need a prescription for insulin. It should read Up to 150 units per day. Please dispense pens.” Clearly, figure out how much you need first and then add in the oooops factor and use that number. And maybe you went the direct and clear route and are still not getting what you need. But persist kindly!
Also this thread might be of interest to you: