gm340 motorola two way radio not working correctley? any solution?

Hi

i was hoping someone may have any suggestion, i have a gm340 motorola two way radio fitted in my car for taxi, it works most of the time but sometimes it wont work? is this because of the ariel or the wiring?

also i can hear everything my taxi office says to every driver when its suppose to only be set up so i can hear when they talking to me only.

any suggestions… thank you