Does insurance not apply if you ask for additional 2 months of medications to take on a vacation?

Hello, I don't know much about insurance and I am also trying to assist my relative who doesn't speak much English.

Anyway, she tells me she pays about $20 for a medication and she asked the doctor for 3 months because she will be oversea. Anyway, doctor forgets to order 3 and the pharmacy only gave us one month supply. I was told to call her insurance and ask them to override something to request for 2 months more batch which I did (When I spoke to the insurance, this is when I learned that her doctor ordered only 1 instead of 3) and they gave me a week to wait. Anyway, few days passed and now my relative told me she got a call from insurance that the total will be $300 (instead of $20 x 3 = $60…)

Does insurance not apply when you ask for additional batch in advance? Should I have called the doctor instead of the insurance to order the extra 2 months (The pharmacy suggested me to call the insurance…)?

I am so confused and overwhelmed, and any help would be great. I will be calling the insurance tomorrow for her but I wanted to try to get some perspective and insights on why it costed $300.

submitted by /u/pewpewpepwpow