Hope it wasn't the dealer that sold the car giving you the oil change info. That was the case with the previous version of the smart (the 450) but as pointed out above, not the case with the new version (451.) Any good auto mechanic can do the oil change - doesn't have to be the dealer. All you need is synthetic oil (Mobil 1 or equivalent), 0W-40 or 5W-30, and the right oil filter - available from a smart dealer or you can get the aftermarket filters from an auto parts store:
Mobil 1 M1-108 (Champion Labs)
Purolator PureOne Premium Plus PL14612 (full fleece)
K&N KN147 (Champion Labs)
Bosch Filtec 3300
AMSoil EAOM103 (full fleece)
to name a few.