It would be natural is under the following conditions:
1. Joseph knew that John was calling him (recognized his voice) He didn't confirm who was calling, so we know that he knows who is calling.
2. Joseph had been waiting for some important news from John (for example, a test result) By saying "Tell me" it implies it was some important news that he had been waiting for because he didn't say anything like "what's going on" or wait for John to say something.
3. They were friends. By skipping the normal polite social interactions, it implies they are friends, otherwise the caller might think Joseph was very rude.
Without those conditions, this is how the conversation likely would have gone:
John: Hello, Is this Joseph?
Joesph: Yes. Hi John (or Is this John? or Who is this/Who am I speaking to)
John: I have your test results!
Joseph: TELL ME! :)
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