Bluetooth malfunction - help sought

I'm a bit of a numpty when it comes to how things work, so please bear with me! I left office last night and used the voice recognition to make a phone call over my OEM Bluetooth kit. A little later into the journey and I hear my phone (iPhone) ringing in my pocket but in-car system doesn't pick it up. I then try to make a call by voice recognition and it all works except once number is dialled the system cuts out. Tried it again today but same problem - wont pick up on incoming calls and will dial-up for outgoing calls but then cuts out so that radio comes back on. Anyone any idea as to where problem could be? Thanks in advance.

Sarge.