Problem! please help.

Hi, Im wondering if anyone has come across this problem before?

I have just finished installing a new head unit door speakers and sub in my octavia

however the sub is all connected up properly and seems to be working ok yet I cannot

control its volume ect through the head unit like I should be able to. I was led to beleive

this is down to the remote cable being connected wrongly but I cant see anywhere else for it to go.

If its any use the head unit is a sony Sony MEXBT3800U

and a vibe cbr 1300 sub

Thanks.