Saying you have proof when you don't is a way to try and get someone to admit to it. We've all used that tactic in the lead team at least once, you have, I have, just about everyone has. Plus there's a difference between an app call (whatsapp) and an actual phone call. All it looks like is he tried getting you to admit to it to see if you did it and had you downloading them as some merit to confront you about it to try and get you to admit it even though now it was found that you didn't do it. Also, I'm pretty sure there is a way to not get notifications of calls etc from the app, at least there should be.