How should I report fraudulent calls made supposedly from Microsoft?

I received a telephone call from  a Sandy (supposedly from Microsoft) informing me that my computer was on the verge of becoming inoperable because of several viruses. They claimed they had been alerting me via computer about these viruses but to no avail. If I did not speak with them then they would just call again requesting the same informtion. I have been trying to call Microsoft to provide information given to me from this person but the process is not user friendly.