I got ****med - service lie and imperfection

I took my car for service at The Glen VW and when they finished everything I couldn't see that my car is now having a dent on the front fender. Since i took it and drove off the garage before i could lodge a complaint, I then accepted my negligence and called my maintenance plan holder. They referred me to Automagic for resolving the problem of my front right fender. I took a picture of the fender to send to the Maintenance Plan holder of which Automagic is also in position of. 0n the 23rd of October 2018 the car was received at Automagic to remove the dent. After 5 days they called me to come collect it and the dent was no longer there. after few weeks without any impact exerted by anyone nor collision, the dent reappeared and I felt so ****med.

As an attempt to solve the problem I went to Automagic on the 28th of March 2019 and they chased me back saying that it is my fault, it is no longer their responsibility anymore because the dent was new even though it is the same dent reflected on the pictures we both have (of before they fixed as the assume). I am very annoyed and I really want justice on this