CBT stands for Connectorised Block Terminal. They range from 4 to 12 Port Blocks.
It’s basically what your Overhead or Underground Fibre Cable will attach to before it goes to your property.
Not sure what they mean by Rebuild. They are built in a factory in Poland.
I’m guessing what it needs is a CBT Shift. It may have been put in the wrong location, i.e. on the wrong Pole or in a Joint Box when it should’ve been put on a Pole. Basically a Shift is where they’ll come out and move it to where it should be or a better suited place than it currently is.
Of out interest where so you live because I know of a few CBT’s that have been put in the wrong place where I work.