1. I've really got to go, I'll get back to you when I get the office.
2. Sorry, I've got to hang up. My wife's waiting for me.
3. Sorry, I must end the conversation. There's someone on the other line.
4. I think I'd better let you go. I'll talk to you later.
5. I have to get back to work. I'll call you later tonight.
6. Shall we continue this later? I've got a call waiting.
7. Sorry, it's getting late. Can you call again tomorrow morning?
8. I've got to meet a client right now. Can we talk later?