Son not hanging up

[Samwelly]

My friend's 7 year old son rang his Mum's mobile from his Nanny's phone. When his mum didn't answer, he left the BT landline phone phone off the hook. My friend is now really worried. Will BT charge them for the four hours the phone was off the hook?

If it went to answer phone I think it only has a maximum of 10-15 minutes on there then would automatically cut off.

If it just cut off there will be no charge.

It needs to be connected for the call to be charged for.