I think in North America it’s illegal for a dealership to force a customer to bring the vehicle to them for maintenance. They can require you to prove it was maintained per the owner’s manual but any licensed mechanic can do the work. The dealership can't force you to only go to then for maintenance by threatening to invalidate your warranty. It's why Mercedes vehicles don't have drain plugs on oil pans so only they have the ability to perform an oil change. Regular oil change places don't have the equipment to vacuum the oil out through the dip stick hole like Mercedes dealers do so you must take it to them for all oil changes. If they could simply force you to bring it to them they wouldn't have gone to great lengths to remove oil drain plugs.