Hey there,
I don't know your dog's age or anything about your dog.
If cropped in the US this is done when they are young puppies. Many reputable breeders crop the litters before placement so it isn't left up to the buyer to decide if they want to crop, who will crop, how to handle the aftercare, etc. That way their puppies are cropped by experts and have the best care during the procedure and have good crops. However, there are some breeders who don't crop before placement and leave that up to the buyer's expense if they want to do that.
It is hard to find a cropper period. It is even harder to find an expert cropper for Doberman ears, most croppers can do short Pit crops but aren't really skilled at making each crop match both the breed and the individual dog itself. There are only a few in the country that do wonderful Dobe crops. A bad crop can really affect the look of the dog, as can improper aftercare. The aftercare on crops can take months in some cases. Cropping requires dedication.
I see you are new, if you want more information on this subject there is a search function you can use to get more information fast.
Hope this helps.