LoLAcademy, How do they keep getting on my freindslist

Ok so after playing a few games today i got a message from one of the many accounts of lolacademy and I'm just wondering how they keep getting on my friends list because it happens to be really annoying to see them message me. So heres what i want to know, how many other people are pestered by lolacademy and its like and also how to permanently get them off my friends list.