My 2018 Ford Edge is blowing cold air in the back and hot air in the front. How do I correct this?

What is your question?

My kids are freezing when I use the heat. The front has heat, but the back has cold air blowing every time we use the heat.

How long has your 2017 Ford Edge had this problem?

Just noticed the issue this month. Got that car in Jan 2018. Don't recall it being an issue when it was cold last year.