A/C problem

When I turn my A/C on on the lowest setting the A/C light comes on but there is no air. When I turn it to the other three settings the light goes off and it blows hot. Also, my radio does not work and I have checked all my fuses none are blown. About six months ago someone was replacing my battery while I was over seas and they crossed the cables and it blew out the alternator, ever since then nothing seems to work. I did not know where I should start to diagnose the problem because before that happened everything worked fine. Thanks