BT phone operators are visiting schools this week to warn pupils against making fake emergency calls to the 999 number.
They're worried as thousands of the hoax calls made every year are thought to be made by children who may not realise they could cost lives.
Services like the fire brigade, ambulance and police waste loads of time reacting to false alarms.
This means that real emergencies are sometimes dealt with later, which could put people's lives at risk.
BT workers will visit schools around the UK showing a special video which warns of the dangers of making hoax telephone calls, and ask children to think twice before dialling 999.
Of the 30 million 999 calls handled by BT, 52% were hoax, made by accident or not suitable for the police, ambulance or fire brigade
People who deliberately make a hoax call could face up to three months in prison.