If you are unable to remove the car from protection with keychain, check whether it is working condition (very often the cause of the fault becomes of the discharged battery). Replace your old and then try to repeat their actions.
The signal that is coming from the remote control directly to the car can be "smothered" by extraneous signals, in this case, get as close as possible to the car and again try to disable the alarm.
If the previous two steps did not yield positive results, then determine the type (by name) installed on your car alarm. Depending on this, will be selected in subsequent steps.
Open the car door using the key (in this moment should trigger an alarm and to turn on the Parking lights).
Turn on the car ignition.
Look in the cabin and push-button Valet switch car alarm (usually in the standard version, this button is located near the driver's footwell, directly under the steering wheel, the back side of the steering column near the Parking brake or under the driver seat).
After ten seconds press the off button alarm Valet, it will give the option to disable the alarm and start the car.
Use a personal code, if any. Open the car using the key. Enable, disable and re-enable the ignition. Press the Valet button the number of times corresponding to the first digit of Your code. Then shut down, and then again turn on the ignition and press the Valet button the number of times corresponding to the second digit of the code.
In any case keep calm and follow the sequence of the actions listed. If they don't help, you should not deal with Amateurs. Call service to deal with the problem will help qualified professionals.