What should i do if this older man wont leave me alone?

a while back i made myself a moco space after fiding out how discusting it was i deleted it but after i did an older man txted my phone asking me who i was and telling me how pretty i am i asked how he got my number and he said he got it from my old page before i deleted it well ive asked hime to leave me alone but he thinks were destined to be together and how im the one for him so im getting ready to change my number just not too long ago i had a random tex message from him saying hes been watching me and he cant wait to see me i fliped out im scared what do i do im 18 this guys 31