Unwanted chat

Hi! I need some advice here please. So the RSP texted me earlier saying if we could have a chat soon. I obviously have 0 interest and Im not gonna pretend to be like “yeah maybe..” i want to say no but in a polite way. Also, I’m aware “no” is a full sentence but i don’t want to sound harsh or anything. Ive been out for over a year now if that matters. Thanks in advance :)