The phrase "firmly reminded" is correct and can be used in written English.
You can use it when you want to emphasize that someone was reminded in a strong or assertive manner. For example: "She was firmly reminded by her boss to complete the project on time." "The teacher firmly reminded her students to study for the upcoming exam." "I was firmly reminded by my doctor to take my medication as prescribed."
By the end we are firmly reminded that nothing is sacred, least of all family.
Speaker J. Dennis Hastert took the rostrum as the debate opened, and firmly reminded the chamber that rules prohibit use of abusive, "profane, vulgar or obscene" language.
Sandra Annette Bland was the fourth of five daughters, whose mother, like mine, lovingly but firmly reminded her, "I'm not here to be your friend".
In September 1969, several months after Bowie Kuhn's election as the commissioner, Miller amicably but firmly reminded him that Kuhn's role was to represent the owners, not the players, and that he could not be impartial about player-owner relationships.
You can be a 39-year-old shortstop with devotees sketching out your Hall of Fame plaque and be firmly reminded that you are overstaying your time in a young man's game.
We had had a minor panic attack when Scott and I realized we had forgotten our passports -- yes, you do need one to get into the Bahamas, as we were firmly reminded by the customs officials in Abaco.
— Just 32 miles from a place called Hope, this small working-class city at the Texas and Arkansas border is "Clinton country," as people here frequently and firmly remind you.
So touchy is 10 Downing Street about this question that Prime Minister David Cameron took time during a 30-minute call to firmly remind President Obama that BP is a global corporation, and that it long ago ceased calling itself "British Petroleum".
One minute you're sitting at your desk, happily wallowing in a universe of dread and fear of a magnitude that only a truly self-absorbed person (that is, a writer on the verge of publication) can fully imagine, and the next your mother is firmly reminding you of the real world.
But he knows - and Nicola Sturgeon gently but firmly reminds him - that Scotland tends to prefer discussion to diktat.
Mojaddedi confronted Karzai after the president joined him on the stage, firmly reminding him that the U.S. had given written assurances on so-called U.S. night raids.
