Many times and in different formats. You can call them, some have an online chat option, and you can also text certain numbers.
All different experiences, even if you use the same service. Depends on the person. Some just go through standard boring questions, some will actually talk to you about the problem you're facing, sometimes the calls are long, sometimes they're more brief. Once, I was texting the national US crisis line and the person was repeating what I was saying, but getting everything totally wrong and not understanding me, so I STOPped the conversation after I already said I would kill myself that night. They sent police. But that was the only time that ever happened.
So your experiences will vary. They can be good for talking you out of a crisis. Remember, you don't have to be suicidal to reach out, or even be having thoughts of self-harm, if you just feel overwhelmed and above a 5 it's totally fine to call or text as well. Even if the call doesn't go well, they can still point you to the more appropriate resources, such as behavioral health resources, as well as inpatient options, and of course while you stay they set you up with outpatient care.