A.
It is not always necessary to change the verb when you use reported speech. If you report. something and it is still true, you do not need to change the verb:
* direct: Tom said ‘New York is more lively than London.’
reported: Tom said that New York is more lively than London.
(New York is still more lively. The situation hasn’t changed.)
* direct: Ann said ‘I want to go to New York next year.’
reported: Ann said that she wants to go to New York next year.
(Ann still wants to go to New York next year.)
Note that it is also correct to change the verb into the past:
* Tom said that New York was more lively than London.
* Ann said that she wanted to go to New York next year.
But you must use a past form when there is a difference between what was said and what is really true. Study this example situation:
You met Sonia a few days ago.
She said: ‘Jim is ill.’ (direct speech)
Later that day you see Jim. He is looking well and carrying a tennis racket.
You say: ‘I didn’t expect to see you, Jim. Sonia said you were ill.
(not ‘Sonia said you are ill’, because clearly he is not ill.)
B.
Say and tell
If you say who you are talking to, use tell:
* Sonia told me that you were ill. (not ‘Sonia said me’)
* What did you tell the police? (not ‘say the police’)
Otherwise use say:
* Sonia said that you were ill. (not ‘Sonia told that…’)
* What did you say?
But you can say something to somebody’:
* Ann said goodbye to me and left. (not ‘Ann said me goodbye’)
* What did you say to the police?
C.
Tell/ask somebody to do something
We also use the infinitive (to do/to stay etc.) in reported speech, especially with tell and ask (for orders and requests):
* direct: ‘Stay in bed for a few days,’ the doctor said to me.
reported: The doctor told me to stay in bed for a few days.
* direct: ‘Don’t shout,’ I said to Jim.
reported: I told Jim not to shout.
* direct: ‘Please don’t tell anybody what happened,’ Ann said to me.
reported: Ann asked me not to tell anybody what (had) happened.
‘… said to do something’ is also possible:
* The doctor said to stay in bed for a few days. (but not ‘The doctor said me…’)