Product: Credit card

I made a 0 % balance transfer on my Barclays Mastercard account in the amount of {$6000.00} on XX/XX/XXXXXXXX  which expires XX/XX/XXXX. I have been making payments in the amounts of {$250.00} - {$600.00} or more to pay the transfer balance in full by the expiration date. On XX/XX/XXXX I initiated another balance transfer in the amount of {$1500.00} which expires XX/XX/XXXX. At that time, I had a balance {$3300.00} remaining on the first transfer. On XX/XX/XXXX I made a {$500.00} payment with the expectation of it being applied to the first balance transfer due to expire in XX/XX/XXXX. However, my XX/XX/XXXX statement showed that my 2nd transfer had a balance of {$1100.00} although it had not even been a month since opening it and the first transfer had a balance of {$3000.00} which meant only {$220.00} of my {$500.00} had been applied. When I contacted Barclays, I was told the computer determines how payments were applied since both had a 0 %. I complained at that time they were forcing me to make accelerated payments ( paid {$2500.00} on XX/XX/XXXX and {$950.00} on XX/XX/XXXX ) on both transfers to make sure I did not miss the XX/XX/XXXX expiration and that I should be refunded some, or all of, the second transfer fee since I was not getting the benefit of the promotion. I spoke with multiple employees to include a supervisor about the issue with no resolution and received the same reason that the computer decides how to apply the payments which they can not override, although the agreed with what I was saying. In speaking with customer service in XXXX I was told when within 60 days of the promotion expiration, the payments would be made to the promotion due to expire within 60 days. Yet as mentioned above the XXXX payment didnt go entirely to the XXXX expiring promotion, the computer elected to split the payment. I was also told the balance of on the {$6000.00} transfer was only {$370.00} yet that was not reflected on my XXXX statement. In reviewing my XX/XX/XXXX statement there was a balance of {$840.00} for the first transfer ( not {$370.00} as stated by customer service ), so I made a payment on XX/XX/XXXX in the amount of {$950.00} to ensure the first promotion was paid in full prior to expiration on XX/XX/XXXX. I then called Customer Service the same day and was told they saw the payment pending and told me my promotional balance was {$370.00}. It was not until this call that I questioned them about the discrepancy in the amount given by the agent and what was reflected on the statement, because I was assured previously my XXXX statement would have the updated balance. On this call customer service did some research and then told me the statement shows the amount subject to interest if not paid in full but is not the balance of the promotional transfers ( it's not clear from the statement how the balance subject to interest is determined ). I asked for written documentation of my transfer balances rather than having to rely on calling customer service, because the balance subject to interest is meaningless without knowing what balance needs to be paid. I was told that information can not be provided to me, it is only available to the company via their system. I find it COMPLETELY UNACCEPTABLE to not have written documentation about balances that I am paying on. Additionally, my balance for the {$1500.00} transfer has changed from {$1100.00} on the XX/XX/XXXX statement back to {$1500.00} on the XX/XX/XXXX statement without explanation. I have no idea how Barclays is making decisions on these balances. My complaint is three-fold : ( 1 ) I should be able to have my payments applied, first, to the promotion that expires earliest and then the later promotion when both have the same 0 % APR, not be at the mercy of the arbitrary selection by their computer, ( 2 ) I should have written documentation of the balances I am paying on and ( 3 ) the amounts reflected on my statements have changed without explanation. The current statements are misleading and incomplete which I feel is intentional and designed to make it harder to track timely payments of the transfer balance subject to hefty interest rates if not paid in time.