Don't worry. This is the solution.

If you didn't get any responses from your HR and they didn't send you an updated offer letter which follows your requirement. You can just use the offer letter they gave to you and go to sign the TN visa on the border. Remember google and check the offical web site and see what the other materials you may need to show to the border officer.

A lot of HR personnels may not know that many details on TN Visa. You either educate them or get all other documents ready with the offer letter and explain well to the border officer. Normally it is just a piece of cake if your professional position is on the TN visa list.

No worries. Good luck!