What to do when u are constantly being hit on by an older dude?

Like this dude has been hitting on me since last summer. I have kinda blown him off but after a year he hasnt gotten the hint. Like i volunteer at a local monthly event that happens in my town and i met him while i was walking with a female friend of mine, and the first question him and his friend asked if me and her were dating. Since we weren't, we said no, and his friend mentioned he was gay, and I was like cool. But ever since then, he has been trying to get my number even tho i have defelected it every time. He has just been super persistent and i lowkey am just pissed off but i dont know how t get him to leave me alone?