Can someone call and get you fired?

Yes. If you work in an "at-will" state, then the employer does not need any reason to terminate your employment so long as they don't do it for a bad reason. (Discrimination, whistle-blower, etc.) As a result, if your employer receives a complaint phone call from someone, the employer is well within his or her rights to terminate your employment. Keep in mind, office politics may be bad for business, but they are not against the law and neither is being abrasive and unpleasant. So your boss can be a "jerk" and still be well within his rights to terminate you for no reason at all.