Called my cell but I didn't answer.

Received several calls from this number. When I answer the phone; no one speaks and I do not know how to block the number.

If you have an iPhone, there is an option in the settings menu to block a caller. If you have a Panasonic cord free handset land line, you can look in your manual (the manual can also be found online) to get the specific directions for blocking calls.  Only blocks about 30.   If Comcast is your service provider for your landline, they can block approx 30 calls.  I googled the instructions on line to learn how to do it, but you could call comcast too.  Possibly other carriers provide an option to you for this as well.