Heater blows strong in the front and blows cold air in the back

What is your question?

Just had the car serviced at the dealer as we had a coolant leak. When sitting at a light the car would blow cold air but once the vehicle moved, it would warm up again. Front works great and the heat blow when stopped but the back blows cold

What makes this problem better or worse?

Nothing

How long has your 2013 Nissan NV2500 had this problem?

My wife’s car so not sure how long