I want to add something here: The pharmacist (or whoever you are transferring the call to) may find it more efficient not to have to listen to the story twice: once from you, details of which still may need to be clarified, and then again from the customer. It's faster just to get the customer to explain it.
It reminds me of a discussion I had with a receptionist in a small 5-person office I worked in. She was just learning the job and English wasn't her strong suit. So she would listen to voice messages that were directly for her boss, Tom, and sounded to be of a personal nature, as in "Hi, this message is for Tom, I got your message and I'm calling to let you know that (insert detailed explanation of things of a social nature) and if you can get back to me and let me know if you can make it to my daughter's recital on the 25th, let me know."
(Her job was to take calls from clients, as in, "Hi, I'd like to book an appointment with Tom" and she would not relay that to Tom, but book the appointment on his behalf)
She would agonize over getting the details of these personal calls right and ask me to listen to it so I could decipher what was said (thus, taking time away from my work) and I would tell her, "Look, just save the message and tell Tom to listen to his saved messages." But there was some cultural thing with her, as in she felt she had to take every message down and relay it to Tom herself. It's woefully inefficient when Tom can just listen to it himself.