C240 Transmission trouble?

3 months ago, my 2003 C240 Mercedes made a high pitched wine and would not accelerate more than 15 miles per hour and if I did go faster the wine got lauder and higher in pitch. I took it to the local “foreign car” auto shop (I have had the car serviced there in the past) and they replaced what I believe that said was a “contact plate” something that controls the transmission is what I think I remember.
Yesterday (just 3 months later) the exact same issue is occurring. Again I had it towed back to the auto shop and now they tell me the transmission is shot and they will need to replace it. They added it has nothing to do with the plate they replaced/installed 3month ago and they will give me a credit on the plate that installed 3 months ago. Are they correct? Are they telling me the truth? Your thoughts?

It sounds like you’re saying the transmission won’t shift out of first gear. It could be that you need a new transmission, but there could be other causes. It will be hard for any of us here to say for sure.

It would be nice to get a second opinion from a good local transmission shop (not a chain), but that would be expensive if you can’t drive the car now.

Has this transmission always been maintained properly? Has the fluid always been pink or red and at the right level (assuming that this isn’t one of those cars without a dipstick)?