Hi Dev. G, well done for being suspicious, you would be amazed how many users fall for this!
This is a well known Tech Support SCAM - Microsoft will NEVER cold call you!
All they are trying to do is get control of your PC, they will cause your PC to become corrupt and then require you to pay to have it fixed and even though you might pay them, they will not fix it!
Do not give them Remote Access to your PC
Do not give them any personal details
Do not pay them