Please healp with my automatic transmission problem
My CLS has been idling for close to 3 weeks at a dealer workshop because they cannot get my transmission right after I sent it in for oil leak and jerking on slowing down on two occcasions. they changed the oil, replaced filter and worked on the solenoid. they kept it in the workdhop because they needed to check the oil at a cool temperature i was told. after collecting my vehicle I drove it for 2 km and realised that there were now new issues, including thudding and lagging behind on acceleration and deceleration. I took the vehicle back and now I have been told they need to overhaul the whole gearbox system.

I may be naive but feel they probably are clueless in what they are trying to do. Where can I get more convincing help. please advice

regards
muks