Friends who annoy you - What can you say to them?

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I have friends that annoy me in various ways, not just one off things, continuous things. Such as one who always feels the need to call/msg me 24/7 about just anything or saying they want to 'catch up' everyday. Sure its good to talk etc, but its a little too demanding and over the top. If I don't reply they'll msg me again asking where I am or why aren't i replying! What can I say to them for them to ease up on the communciation or just stop?