I'm Tatsuya Shimomatsu and I'm a voice actor. Sorry for doing this by phone, but you know how it is. I can't damage the image people have of my characters, so I don't show my face very often.
Do you see any errors here? Are there any other expressions interchangeable with "you know how it is"?
It's correct language. Not using "I'm" before "sorry" is something typical of spoken English. I wouldn't say there are any real "errors" to speak of unless the grammar police want to write Tatsuya a ticket for saying "sorry" instead of "I'm sorry". It's okay for spoken language and an informal email or informal note. I'd be cautious of writing this in other situations, however.
I think "you know how it is" is the best phrase for this short spoken language text. I can't think of anything better, and I don't think it's necessary to do so.