Read your warranty paperwork. Unless it says that you must take it to a dealer for all service, you can do exactly what sm1ke & Buzz say. Do use a factory oil filter. Engine makers do not publish the specs for the oil filters. Aftermarket filters are reverse engineered to match...or come somewhat close...to the performance of the OE filters. In the unlikely case of a failure of an engine lubricated part, you don't want to give the car maker any ammo to try to deny a warranty claim.
Oil filters need to fit correctly--thread size, gasket size, can size--plus can strength, filter media filtration specs, internal bypass valve specs, anti-drainback valve. In some cases aftermarket filters are excellent and made for the engine. In other cases the filter maker just picks some existing filter from their catalog and lists it as "suitable" even if it's not an exact duplicate. (The internal bypass valve is necessary to bypass thick cold oil that would rip the filter media and to bypass in case the filter media is clogged with crud--unfiltered oil is better than no oil to the engine. The bypass valve works on the pressure differential between the filter inlet and the filter outlet. For example, the WIX 57002 (and NAPA 7002) that fit our cars has a bypass filter that begins to bypass at 11 psi-differential and is fully open at 14 psi).
20,000 mile service? Check your owner's manual for the service specs for when and what is required. Don't let the thieves at the stealership sell you unneeded service.