In XXXX I opened a new credit card with Navy Federal Credit Union. The card had a promotional rate of 0 % for balance transfers for 15 months. Once I opened the account I decided to use the card for all of my purchases in addition to the {$9700.00} balance I transferred in. I called customer service and inquired as to how payments were applied to balances and how interest was charged. I was told, in XXXX, that if my purchase balance was paid in full each month by the due date, I would not incur any interest charges-regardless of the promotional balance because the promotional balance had a 0 % interest. For the last two months I have been changed interest by the credit card company, even though I pay off my entire purchase balance each month ( and then some to bring down the balance transfers XXXX. 
When I challenged the company this past month, they explained to me that even though their " statement disclosure '' states that " We will not charge you interest on purchases if you pay your entire balance by the due date each month, '' they claim that they calculate interest using the " average daily balance '' which takes into account the balance transfer ( even though the balance transfer has a promotional rate of 0 % ). 
The terms of their agreement are deceptive and I believe how they are charge/calculate interest is deceptive and intended to confuse customers in an attempt to charge interest on promotional balance transfers that are allegedly 0 %. Their own customer service staff were perplexed why I was being charged interest and were largely unable to explain how I was being charged interest when the purchase balance was paid, in full, each month and the promotional balance transfer rate was 0 %. 
