Suzuki Swift 2009: Speed bump squeak

My 2009 Suzuki Swift has an annoying squeak coming from both front and rear ends every time it goes over speed humps and undulating roads. The dealer keeps saying it is beach sand in the struts etc and they have cleaned and re-greased the both ends of it. But the squeaks are still there and I feel they are just giving me a snow job. The car is always garaged and has never been to the beach. It has done 26,000 km and is coming up for its 30,000 km service. Any advice please?