Can a recorded telephone call be used as evidence?

The short answer to your question is that it depends.  The rules of evidence are very complicated, and their application in any given circumstance depends on the particular set of facts.  For example, a statement of a party to the matter (such as the plaintiff or the defendant) might be admissible, whereas a hearsay statement (made by a third party) might not be.  In any event, if the recorded call is relevant, you can be assured that the attorneys involved in the case will have argue both sides of the admissibility argument.