Vlad, what makes you think this is "номер офиса, а не личный"? I think it can be both depending on context.

If you want someone's # you would ask for it. "people can call" indicates that you are looking for # public can call.
E.g. I have a friend and want to refer another friend of mine to her for business. I would use this exact sentence. I already have here personal #, I need a # for business. They can be one and the same of course.

Vlad, why is this necessarily an office? This could be a hotline, a help line, a technical assistance line, a call-in line for a radio show... the list goes on. Also, the original English question is kind of strange. Normally, we would ask "Is there a number we/one can call" - but then ALL telephone numbers are for calling. So the question here is context. Where did this come from and what does it refer to? I don't think anyone can translate it as is - it's a mystery. Russ is right.

This could be a hotline, a help line, a technical assistance line, a call-in line for a radio show...

Exactly! Not your personal number.