I have to hop

The line one rolls out when one can no longer bear the conference call, but there seems no less brazen way of engineering an exit. It implies you have something better to do — it's a matter of irrefutable mathematical logic that one has something better to do, if what one is currently doing is attending a conference call — but doesn’t commit you to articulating anything an unemancipated fellow participant could cast judgment on.

There are more or less snarky variations, the best of which is “I have to hop: I have an industry call starting” — the office worker’s equivalent of “I’d love to stop and chat but I have to go and wait in the lobby”