Paphos Life

I need some help, A few months ago I accepted a friends request from a guy called Buster, as we both had an avid interest in the 70's band The Sweet. He sent me the odd video of the band but then he started to bombard me with not only videos but almost non stop messages on Messenger......now as much as I like The Sweet I thought enough is enough and so I tried to unfriend and block him but I was unable to.....this is where I need technical help ...
Does anyone know the way ....there's got to be a way, to Block Buster ?