i refuse to answer have no idea who it is

This number called my cell phone while I was on another call. I ignored it. The person did not leave a voice message.

I received several calls on my cell from this #. They never leave messages.  Finally answered and it is some sort of travel type business pushing "discounted Branson, MO vacations". When I questioned the guy about calling a cell number he was very rude.  When I told him he was rude and requested he delete my number from his calling list, he responded with how rude I was. I hung up and will never answer another call from this company.