Asus India — asus service issue

Address: 560066

Booked a complaint with asus for service. Asus provided third party service enginner, who took my laptop and lost all my data. When i contacted asus service center for support they said they cannot do anything. How come the service engineer lost my data without even intimating me. Tried contacting asus no of times to help recover data and told them no of times that data was very critical, in spite of follow ups, they didnt do any thing, they misbehaved as well