I worked in call centers (airlines, tech support) for much of my adult life and it's always been the case that workers were expected to take calls until the very end of their shift. if that meant they ended up staying a half hour late, so be it (and would get paid for it, of course). That possibility is part of the job. If you had something really important that evening and absolutely needed to leave on time, you could asked to be assigned to do paperwork or emails for the last hour so you could log off on time, as an exception.
Now, as an end user if I have an issue I suspect takes an hour, and I know the callcenter closes at 5pm, I'll try to call in before 4pm. But I may not have time, or the case may take longer than I suspected, and I am not going to feel rude or guilty about it.