Air Conditioning is Hot!

[DCVolvo517]

I have a 2007 Volvo S40 with about 61,000 miles. It has received all of its annual maintenance every 7,500 miles. Today, I was driving around doing errands. I turned the car on and off several times, and the air conditioning was very cold. I turned off the car and turned it back on an hour later. This time the AC was blowing nothing but hot air, and the warmer you selected the air, the hotter it got - even hotter than heat in the winter!

The only problems I can find are about AC units switching back and forth between cold and warm air, but my problem is it is only blowing hot. I even let the car cool off, went out to the garage 2 hours later, and it is still only blowing hot air.

What could be the problem? I'm a girl, and I'll admit I know nothing about cars. I don't want to get taken advantage of when I take it to get fixed. Thanks.