How to kindly refuse a date?

So, I have been speaking to this guy off Tinder for awhile.
I found him a little strange and he liked to continually phone and FaceTime me. Anyway, cut a long story short, he asked for us to do something but I kindly said Im sorry but I really do not want to be dating at the moment.
That didn't seem to do the trick as he is still trying to talk to me and has phoned me again today and I ignored it and asked him why he called.
He says he wants to know if I wanted to do something sometime.
How do I politely but assertively say ' We are complete opposites and no, thank you '?

Any tips

Tell him he's a nice guy and all, but you don't feel the spark #Moooose

Are you patient zero for Twitter-induced Tourette's, or do you genuinely not realise that your username already accompanies each post you make, thus obviating the need to hashtag-strapline your every utterance like some kind of manically self-fellating Youtube hack?

Honestly, I half expect a fluorescent signature commanding everyone to "smash that rep button!"

I like the whole moose thing. Ignore toxic inputs and focus on bringing happiness and prosperity to the interwebs. #Mooooose

I have already declined a date but obviously I did this a little too gently.
He says he wants to know if I wanted to do something sometime. AGAIN. and is constantly ringing me.
How do I politely but assertively say ' We are complete opposites and no, thank you '?

Any tips

Erm, no #Moooose