I believe you said it was MB Glasgow you bought from ?
I , too , use their parts dept and , as with dealers in Edinburgh , Perth , Ayr and elsewhere from whom I have purchased parts , it is normal policy to tell you that parts not normally held in stock but which have to be specially ordered in then correctly supplied are non returnable .
Of course , if you supply your chassis no ( I usually take in my service booklet with the data card in the back so they have to read it off for themselves ) , then if the part ordered turns out to be incorrect for your car then it is their error and they have to rectify it .
I have never had any problems with parts from my Mercedes dealer , but I once bought a pair of front brake discs from Eurocarparts , I was supplied with two identical boxes , each with the correct part number on the outside - only one box contained the correct disc and the other contained a completely different disc for I don't know which vehicle - however , going back to the store ( ECP Glasgow ) with both boxes plus contents , the invoice and explaining calmly what had happened , the counter assistant could not have been more helpful , apologised that they didn't have another W126 front disc in stock but said he could obtain one for the next day and even arranged for their van driver to drop it off to me to save me having to drive into Glasgow yet again : top service for an error that was down to the manufacturer ( ATE ) and not in any way their fault , so I left with a good impression and still regularly buy from them .
As has been said , in your case the dealer is not obliged to refund a correctly ordered and supplied item , but given that the parts will clearly be unopened and in pristine condition , as well as something for which there should be reasonable demand , it would not be unreasonable to ask nicely whether they might accept them into stock and refund most of what you paid , less a reasonable handling charge - say a tenner or so ?
They don't have to do this , but it would be good PR .
If they won't refund , you could also ask about the possibility of a credit note towards something else you might need for your car ?
I , too , use their parts dept and , as with dealers in Edinburgh , Perth , Ayr and elsewhere from whom I have purchased parts , it is normal policy to tell you that parts not normally held in stock but which have to be specially ordered in then correctly supplied are non returnable .
Of course , if you supply your chassis no ( I usually take in my service booklet with the data card in the back so they have to read it off for themselves ) , then if the part ordered turns out to be incorrect for your car then it is their error and they have to rectify it .
I have never had any problems with parts from my Mercedes dealer , but I once bought a pair of front brake discs from Eurocarparts , I was supplied with two identical boxes , each with the correct part number on the outside - only one box contained the correct disc and the other contained a completely different disc for I don't know which vehicle - however , going back to the store ( ECP Glasgow ) with both boxes plus contents , the invoice and explaining calmly what had happened , the counter assistant could not have been more helpful , apologised that they didn't have another W126 front disc in stock but said he could obtain one for the next day and even arranged for their van driver to drop it off to me to save me having to drive into Glasgow yet again : top service for an error that was down to the manufacturer ( ATE ) and not in any way their fault , so I left with a good impression and still regularly buy from them .
As has been said , in your case the dealer is not obliged to refund a correctly ordered and supplied item , but given that the parts will clearly be unopened and in pristine condition , as well as something for which there should be reasonable demand , it would not be unreasonable to ask nicely whether they might accept them into stock and refund most of what you paid , less a reasonable handling charge - say a tenner or so ?
They don't have to do this , but it would be good PR .
If they won't refund , you could also ask about the possibility of a credit note towards something else you might need for your car ?