Booked Window but forced to move the seats even after paying for the same

Booked a flight well ahead after paying for the windows and middle seat. Even after going through all checkin and security and was sitting on the plane was asked to move seats without any apology.
Promised to have a windows seat in replacement and the luggage to be moved but nothing happened.
Caused a lot of inconvinience during the flight while sitting in Aisle and even had a struggle getting my luggage from ovehead compartment which was 15 rows behind my new seat.