Hello!
This could really seems a stupid question, but I don't know how to contact English lecturers/professors and I'm starting to panic.
I've already been admitted to a PhD, that I'll start in October, but I've never spoke to none of my supervisors (I've only exchanged very few emails).
Now, I need to contact one of them and it's quite an urgent thing. He wrote me he'd be glad to have a chat on the phone too, so....what should I do now?
I already answered leaving my number,etc...then after 2 days without an answer, I called his studio number (there are no office hours AFAIK): no answer and no answerphone.

Do you think I should write another email asking for a phone appointment or should I continue to call? or is it too rude?

If it is urgent, then keep trying to call him. If it isn't urgent, wait for his email.