Issue with speed / Service

On 1/3/2023 I ordered an upgrade on my line from 250/250 to 500/500. On 8/3/2023 it seems all should be fine. From that day till now I don't get what I am paying for! Technician was onsite as they assume the problem is always on your side! He confirmed that the speed is not correct. The problem is thrown between Vox and Frogfoot I measure now less than 100/100!