So, Charlie, where are you? Are you there?
Charlie你在哪里？你还在吗？

Hello？你还在吗？
Yeah. 在呀在呀~

Are you there?
你在吗？

You (still) there?
你还在吗？

Yeah, I'm here.
我在这儿。

Hold on a sec.
稍等。

I thought someone was knocking on my door.
我刚才以为有人敲门呢。

Can you hear (see) me?
能听得见我说话吗？/看得见我吗？

Yeah, I can hear (see) you.
听得到，你听得到我说话吗？

Can you hear (see) me?
看得到，你听（看）得到我吗？

Anyone/anybody home?
有人在家吗？

Anyone/anybody there?
有人在吗？

Coming. 来了。
Who's there? 谁呀？
Who is it? 谁呀？
Hold on a sec. 等下。

Hello? 有人吗？
Anyone there? 有人吗？

Occupied. [ˈɑːkjupaɪd] 有人。
It's taken. 有人啦。