Any that don't involve something along the lines of "give me money and it won't go off"?
https://en.wikipedia.org/wiki/Sam_Melville#Bombings
The IRA also phoned about many of their bombs. The Omagh bombing is mostly notable because their phone-call didn't accurately identify where the bomb would detonate, and so got people killed.
Plenty of terrorist groups have recognized that killing innocent bystanders isn't good PR.
Is it terrorism if they take active steps to prevent terror?
Attacking the enemy and avoiding collateral damage is usually called making war.
I wonder if it's more about phsycology, someone making a bomb threat is seeking attention for some reason and ignoring it might make their behavior escalate.