Before you call for service – Check this 

• Check your breakers, inside and outside. Storms sometimes will trip them.
• Check the switch on the furnace. It could have been accidentally turned off.
• Check the disconnect on the air conditioner unit. This is the box on the outside of the house by the unit.
• Check your filter. Make sure it is clean. A dirty filter can block airflow and freeze up the unit; it cannot be serviced until it is thawed out.
• If you have ice build up on the black line running from the air conditioner into the house, it is frozen up. Shut the unit off, check your filter and change it if needed, let it thaw and see if it starts cooling properly. If not, you possibly have a Freon leak and the unit will have to be serviced.