Qual è la differenza tra I have to call you myself. e I have to call you by myself. e (I also want to know the meaning and when you use it.) ?Sentiti libero di rispondere con un esempio.

I think that by using "by myself," you're emphasizing that it's only you who call, no one else.
Like 'I have to call you by myself, because no one else is allowed to call you with me, or only I can call you'. It feels like it's talking more about the physical act of picking up a phone to call.

If you're just saying that you have to call someone as a response to "Who will call me? Will you call me?" then I'd just respond with "I have to call you myself."

Sorry if that doesn't make sense. I'd say the first one, without 'by', is used more often in more contexts.