If I was involved in an accident in a company vehicle and the person I hit is suing my ex-employer and their lawyer is not representing me, what do I do?

If the person involved is only suing your former employer and is not suing you personally, you do not need to do anything.  If you are being sued personally as well, your interests and your former employer's interests are not necessarily the same, and so you should seek an Arizona attorney to represent you.