er, that is dust.
as for how to clean it, long term to be honest, unless you happen to be the kind who stores his camera in the dry cabinet and never changes lens, best to do diy. where got people have so much time to keep going to the service centre and get charged money for it after warranty over?
there are two types of dust;
1) unwelded dust (no moisture) - this type can be removed by various methods, blower works, sensor brushes (cleaned well) work
2) welded dust (moisture) - harder to remove, needs wet cleaning with sensor cleaning fluid to remove
you should try using blower to remove first, if that doesn't work, and the dust spots do not even budge after a few blows and checks, then time to use wet cleaning. as to how, go google "photographic solutions". first time, if you have no confidence, get someone who has been cleaning his dslr sensor himself for a long time to demonstrate on his own camera for you. if you don't think you're up to it, then keep sending it in, but it is seriously quite silly in the long run imho.