Did you read my guide on wheel fitment?
You are paying a dealer to fit wheels?????
Have you measured how far the bolt comes out of the back of your standard wheels vs how far they come out of your BBS wheels?
Have you attempted to fit them to see the PCD? Where did you buy them, what were they advertised as?
Are the bolt-seat types different between the wheels? Most aftermarket wheel bolt types are different.
If people checked before they did things there would be less surprises for everyone!
http://www.audizine.com/forum/showthread.php/378554-The-Definitive-BBS-CH-CO-RE-Reference-ThreadAftermarket CH types, 5x112
Aftermarket CH's have "motorsport" stamped into the metal around the center and other descriptors on the lip. They only come in Diamond Silver (also known as Bright Silver) or Black with Stainless Lip. All real non-OEM BBS wheels require BBS PFS hubcentric rings and conical lugs. The lower offset fitments have 5 small holes around the center bolt pattern, as Mercedes requires them for wheel alignment.
CH023: 17x7.5 et42. Brilliant Silver. Without alignment holes.
CH003: 17x8.5 et35 Brilliant Silver. With alignment holes.
CH025: 18x8 et50. Brilliant Silver, Black. Without slignment holes.
CH012: 18x8.5 et35. Brilliant Silver, Black. With alignment holes. 26lbs
If yours are genuine BBS kin 5x112 fitment, they appear to be CH025 - so you would need to measure the differences in how much the bolt sticks out, and order the conical bolt types of the correct length.