Software F*&^ UP!!!

My husband took our Polo 2.0 GTI in for a foglight replacement on the 13th of June 2022, he was then called back to say the vehicle had to get a software update. Ever since then the vehicle has not performed like a GTI but rather a TSI. He brought this issue to the attention of the service advisor who could not say what the software update was for but merely that the dealership was acting on instruction from VW Germany. We have gone so far and put in a complaint with VW SA who up until now can still not say what the update was for and why our vehicle's performance has been so drastically effected by a mere 10-15 minute update! We want answers and we want our vehicle back to its original state.