Call forward

Hi all,
i’m freely new to freepbx, but i’ve got the basic configuration working.
One thing we wanted to realize was to be able to forward our phone to a cellphone.
For this i created a custom extension (5300) of which i set the device options to “Local/XXXXXXXXXX@outbound-allroutes”. Now, if i internally call number 5300 i get connected to my cellphone, no problem. Also I can patch through anyone who calles our main number by manually forwarding the call to 5300 and i can answer it on my cell phone.
But here comes my problem;
I configured the call forward of my office phone so that is forwarded to my cell phone. When now someone calles my office phone it is actually forwarded to my cell, and my cell does ring, but when I answer the call, there is a connection established, but there is no sound, I don’t here the other side and vice versa.
Any tips anyone?