the ignition switch was replaced; now when starting the vehicle there is an alarm that sounds and the alarm won't shut off. what can i do?

What is your question?

recent work was done replacing the ignition switch. the day after the work was done, I started the van and an alarm started sounding.....the alarm won't quit until the vehicle is shut off. mine is a 1998 van and nobody can tell me what needs to be done to stop the alarm. I can't drive the vehicle with the alarm continually sounding. 1998 Plymouth Voyager Van....thank you for any help you might be able to give.

What makes this problem better or worse?

alarm sounds when the vehicle is started

How long has your 1998 Plymouth Voyager had this problem?

one week