He had spent seven years sacrificing himself, driving himself to the
    point of breakdown, nearly to death, trying to help these people,
    and they didn’t care about him at all. What was the point? He knew
    that if you were suicidal it was difficult to understand other
    people’s problems, but still—he had been talking to some of these
    people for years, and now here he was dying and nobody cared.

When I volunteered on a suicide hotline, the frequent callers were by far the most disheartening aspect of the job. I believe some of them had borderline personality disorder... at any rate they were highly manipulative, and a large part of the training for the job was about how to avoid being taken in / drained by them. There were one or two people who had figured out the duty roster for the call center, and you would be guaranteed a call from them if you were on duty... multiple hours-long calls, if you let them.

The hotline didn't ban them unless they became sexually aggressive towards female volunteers, I think because they helped keep the call numbers up, which was important for funding.