I just opened the bill for my land line, and found about $600 of charges for calls to 900 numbers that we didn't make. Has this happened to anyone else? How can somebody hijack my land line for this?

OUCH!....Do you have an older son?.....Might want to ask him...OR get on the phone company....and clear up that mess quick

As it happens, yes. He's 13, and denied all knowledge for 3 days. Then I spent an hour on the phone with the phone company today, and got the mechanics of what had happened. It seems the calls were originated to area code 212, then were switched automatically, and without any notification, to the 900 numbers. Armed with this information, I asked my little dear to tell me if he had called any 212 numbers, and, lo and behold, he had. Gotcha. So I 'splained it all to him, including the injunction, which I had thought he had sense enough to know, regarding making any long distance calls at all.

Also put a 900 number block on the phone, which was something I hadn't thought was necessary - after all, no one in my house would be dumb enough to call something that costs $3.99 a minute. Not my house. HA!

I hope he's helping pay for whatever the phone company didn't take off the bill.
Maybe not $600 (daunting for a young teen) but maybe $100-150 (enough to hurt a little, without seeming like a life sentence).
Did the phone co reduce the bill? (seems a 'switched' call should only be charged the rate of a call to the called number)