I already have fibre 1 and have just changed to a new fibre 1 package why do i need an engineer?
Presumably you are moving to full fibre from FTTC which will require a completely new fibre cable and ONT to be provided.
Maybe you're being moved to Full Fibre1.
Welcome to this user forum for BT Retail phone and broadband customers.
Its possible that your exchange is now FTTP priority, so any new order or regrade, has to be FTTP. That would require a visit to run fibre cable and install extra equipment.
Use the address checker on the page below, and post the results, but edit out your address details first.
https://www.broadbandchecker.btwholesale.com/#/ADSL
See if it says FTTP priority, in the notes.