Do you really think that limiting your contact to email and text would be better for you? If you do, of course you can set that boundary. Do not set it as a way to punish though. I would also like to point out that it can be really easy to read into texts etc tones that may or may not be there.
If you need to do this for you, do it. As far as his calls go, what does he call about? If it's mostly (or all) about S, I would at least listen to his message before deciding how quickly to return the call (or text).
