DreamHost does not offer a telephone number for pre-sales or technical support inquiries.
You can contact DreamHost for information via their web-based contact form for pre-sales questions, or you may well find answers to your questions in the DreamHost Wiki or by asking here in these forums.
While I’m not completely sure what you mean by “transfer over”, there is nothing involved in the process of acquiring a hosting account, or moving existing sites, domain hosting, or registration to a DreamHost account, that requires a telephone call; the whole process can be handled via the web.
Should you still have questions after reviewing those resources, there is always the previously mentioned contact form.
It’s also possible that many of your questions can be answered here by other users.