Product: Credit card

My husband and I received a promotional offer for 0 % interest on balance transfers to our Chase United Mileage Plus card. We use this card for many of our daily purchases so we can accrue as many miles as possible and always paid it in full each month. We had a balance on another high interest credit card that was a little over $ XXXX we wanted to transfer that amount to the Chase United card, however were unsure how to pay our new charges, plus the amount owed for the balance transfer in order to keep the 0 % rate on that amount. Before transferring our balance in XX/XX/XXXX, we called Chase 's customer service department to ask how to handle our monthly payments so we could retain the promotional interest rate. We were told that we should pay the total amount of our new monthly charges plus the minimum payment due and and that would ensure we keep our 0 % interest rate. 
Based on this information, we decided to transfer the balance of our other card to our Chase United Mileage Plus card. On our XX/XX/XXXX statement, we noticed a small interest fee charged to our account, but because it was minimal ( {$64.00} ), just figured I made an incorrect calculation on paying off our purchases on the XX/XX/XXXX bill. On our XX/XX/XXXX statement, we noticed that we were charged {$210.00} in interest, but didn't pay our card in full that month, so figured that was how we accrued that interest. On our XX/XX/XXXX statement, we were charged interest in the amount of {$190.00} and in XX/XX/XXXX, we were charged {$180.00} despite paying our bills in full ( minus the amount transferred to the card ). I thought I must be calculating the balance to pay each month incorrectly because when I looked at the table of interest charges on the back page of our statement, the amount subject to interest fees was always higher than our purchases. So, I began paying the balance subject to the higher interest rate on the back of the statement each month plus the minimum amount due to hopefully get rid of the interest charges. 
However, on our XX/XX/XXXX statement, we were still charged {$200.00} in interest. I called Chase 's customer service department again and was told the same information that we were told before transferring the balance- pay your monthly charges and your minimum amount due and you will not be charged interest. For two additional months, we continued to try to figure out the correct amount to pay so that we would not be charged interest on our balance. Yet, on our XX/XX/XXXX statement, we were charged {$150.00} in interest and on our XX/XX/XXXX statement, we were charged {$180.00}. Frustrated and confused, I called Chase 's customer service yet again, and was finally told that having the balance transfer on our account was causing us to be charged daily interest on new charges. We couldn't believe it. We had never heard of this practice before- not from other credit card companies ( I checked our other credit card 's terms to see if this was a customary interest charge we were unaware of- it's not ) and not from Chase 's employees, either. 
I asked for a copy of our card agreement to be sent to us, which we received right away. The agreement states, " If you pay your account in full each month ( or Interest Saving Balance ) in full each billing period by the date and time due, no interest is charged on new purchases month to month. Also, we will not impose interest charges on any portion of a purchase balance you repay while that balance is subject to an interest-free period. Subject to any interest-free period for new purchases, we will begin charging interest from the date a transaction, fee, or interest charge is added to your daily balance until your account is paid in full. '' This is confusing wording because we were paying all monthly purchases charged to our account in full each month, except for the amount that was subject to an interest-free period. That led us to believe that our account would be considered to be paid in full each month and therefore not subject to any interest. Furthermore, the agreement states that daily interest will accrue if there is a balance due to an interest-free period on NEW purchases. Our balance was the result of a balance transfer, NOT new purchases, so we don't believe that our balance transfer should have subjected us to daily interest charges. 
Once we learned this information, we paid off the remaining balance ( new charges plus the remaining balance on the balance transfer ) in XX/XX/XXXX. We didn't complain about the interest charges right away because we thought we had made a mistake, but it just didn't sit well with us. We decided to call Chase on XX/XX/XXXX ( I think ) to complain about these charges and to ask for them to be refunded to us. When we called, one customer service agent told us that she couldn't file a complaint for us and that Chase always charged a daily interest rate on new purchases and that no balances were ever subject to a 30 day grace period ( which is customary for every credit card we've ever had ). Again, we were shocked by this information and didn't believe it was true, so we pulled out all of our past statements and saw that she was clearly incorrect- we had never been charged interest on any charges unless the statement had not been paid in full. We called back a second time that evening and was told that we were only charged interest after the balance transfer was completed because we were carrying a balance each month, despite the fact that that balance had a promotional 0 % interest period. She offered to refund us one of the interest fees in the amount of {$170.00}, but that felt like a drop in the bucket to us. We did not feel like the experience made us whole. 
We try to be diligent with our finances and read through our statements each month. The fact that we were confused by the interest charges and couldn't determine how and why they were being charged, and because this policy is clearly confusing to Chase 's own employees ( we heard three different policies from 5 different representatives ), we believe Chase 's terms are unclear and misleading. If we had understood that our terms would change because of the balance transfer ( either through the promotional wording or through their representatives ' explanations ), we would not have chosen to transfer the balance due to our use of the card on daily purchases.