Contact info for Belasco House Manager?

You can call Telecharge and, if appropriate, they will put you in touch. You don't say what your issue is so there is no way to say whether it is the sort of thing that requires direct contact. If it is a lost and found matter, they will deal with it; if it is an accommodation issue, they will deal with it; if you want to complain about something, they are more likely to have you send an email; if it is a reseating issue, you will be told it is an on the spot issue (or, depending, it might be handled by telecharge/box office.

The Belasco house manager is named Stephanie. She's a sweet, older lady who has always been nothing but kind and accommodating to me.