Hello, I'm from xx Trademark Office. The "xxX" trademark that your company applied for on X, X, XX will expire on X, X this year, and you should go through the renewal procedures. If you don't renew it, this trademark will be cancelled by the Trademark Office!

By saying this, you can attract the attention of the other party. If the other party is not the one who can make decisions, you can say, "Who is in charge of this matter, please transfer it for me, or leave a number for me to ask again." Let the other party think that you are the person who does this, and it will be smoother!