Is the bluetooth built into the Bolero unit or is there a box somewhere, nothing under the seats??

Should be built in, although to my surprise I found out in some markets it is missing (?)

 

Either way, mine has Bluetooth and there are no boxes anywhere - do not get confused with the MK II models...

No mine has it, but it keeps  disconnecting,  it's will work ok for a while  ,  then when the mobile  rings it's on the handset only  instead of through  the unit,  checked on the skoda  site  for updates,  there isn't any. ,  looks like a trip  to the  dealers  ,  as I need it to work  for taking  calls  on tge move 

What year is your car? There is a thread floating with the latest update for the MIB1 Bolero and maybe that will help on your case.

3 hours ago, Jaco2k said:

What year is your car? There is a thread floating with the latest update for the MIB1 Bolero and maybe that will help on your case.

2016 1.4 tsi

So, that's a MIB2 - no known firmwares in the wild.

 

You can also try to do a hard reset by holding down the power button until the unit reboots and seeing if that helps.