Say/tell
The verbs say and tell are used in both direct and indirect speech. We use say to refer to any kind of speech. It can be used interchangeably with tell in indirect speech, but not in direct speech. We use tell to refer to situations where instructions or information are given.
Mary said that the restaurant was closed.
Mary told us that the restaurant was closed.
Caleb said “Good morning.”
It is incorrect to use tell in this sentence.