Given the task definition and input, reply with output. In this task, you're given a story (which contains five sentences only). Your task is to find all the characters which are available in the given story.

Sentence1: Greg received a call from a telemarketer. Sentence2: They offered him an opportunity to renew his car's warranty. Sentence3: Greg purchased the policy for three thousand dollars. Sentence4: A few months later Greg's car broke down. Sentence5: His mechanic said the repairs were not covered under the warranty.
Telemarketer, His mechanic, Greg