Problem with iax trunk callerid

Hi, how are you all?
I`m having the following problem, I have a iax trunk between one asterisk and a FeePBX. The FreePBX is “mine”

The problem is that whenever caller 300 (callerid name = Juan Perez)
from the asterisk calls an extension from the FreePBX through the iax trunk, the callerid name that appears in the extension display is the one defined in the FreePBX for extension 300 (callerid name= Lucía Gimenez).
I don´t know if I made myself clear.

But if for example, extension 301 from the asterisk is not defined in FreePBX, and calls an extension of the FreePBX through the iax trunk, the callerid name that appears is ok.
So I guess the problem is the FreePBX fetchs the callerid name from its own database.

Any help will be appreciated!! Thanks!!!