Reported speech is used to talk about what someone said in the past. The tense of the verb in the direct quote often changes in reported speech.
Simple present to simple past
"You are late", the bos told him.
The boss told him he was late.
Simple past to past perfect
"The shipment arrived at noon", Mike said.
Mike said that the shipment had arrived at noon.
Present perfect to past perfect
"I have seen the samples already", she announced.
She announced that she had seen the samples already.
If the tense of the verb in the direct quote is in the past perfect, it remains in the past perfect tense in reported speech.
"I had decided to accept another job offer before you told me about my promotion", Elisabeth informed her manager.
Elisabeth informed her manager that she had decided to accept another job offer before he told her about her promotion.