Long answer: There is something called "National Do Not Call Registry". You need to enrol to protect yourself.
Unfortunately, this doesn't seem to be mandatory for the telecom operator to put new numbers in NDNC registry. While filling up the forim while applying for a new number, you need to select the option that you want to enrol your number in the NDNC registry. Unfortunately, most telecos take 45-90 days to effect this. By that time, your number is already "sold" to a lot of SPAMmers.