I purchased multiple items from Best Buy over the last several years. Items such as TVs, home entertainment systems, Computers, etc.
Each item had the "no interest" promotion as long as monthly payments made on time and balance paid off by a specific date. I made all the required payments by the dates required yet the added the deffered interest charges back to my balance after the promotion date ended. Prior to my purchases, other had told me about this practice. I didn't listen.
I am done making in more purchases from Best Buy. This is a warning to others.