Is there any solution to prevent marketers from calling you on your mobile

How many times have you been annoyed by those care loans and home loan offers on your mobile ?
It has become intolerable for me.
I need to know, if anyone with technical knowhow in mobiles can provide some solution whereby I can just block those marketting calls. Unfortunately I don't have postpaid connection, so such technology is not being provided by services provider. may be a software or so to filter such calls as spam or similar, may help. Anyone with a clue ?