Product: Credit card or prepaid card

On XX/XX/XXXX I decided to take advantage of a balance transfer offer. I have very good credit, I owed about {$2400.00} on a XXXX XXXX Credit card, and the card was in good standing. Capital one had solicited me an offer saying I was " pre approved '' for a quick silver capital one credit card '' with a 0 % 15 months offer on purchases and balance transfers. I was just about to put in a new AC unit and was sure I could make the timeline and pay off the card in 15 months. The ac unit ran me about XXXX and the balance transfer was another {$2400.00}, so {$9400.00} decided by 15 months is about {$620.00}. No problem I can do that. So I proceeded to fill out there friendly Little app, all it pretty much asked was the card number, amount and payment address. I thought wow that's almost to easy, ( was I in for a surprise ) immediately I see an email saying my balance transfer request is processing and under review, soon I see an approval, within a few days they were happy to add it to my balance. Wow what service! Right? No! 
I'm someone who keeps a pretty close eye on my credit, and my cards I was checking my XXXX XXXX Credit card every day, I wanted to make sure the card was paid off and if not in a sufficient manner so as to avoid a missed payment I was making a payment, weeks ago by. So I'm concerned and decide to call XXXX XXXX, they assure me saying these things take time, call back in a few days if I don't see it clear. Okay, I figured sounds reasonable, so that's what I did. Several weeks ago buy. Nada, nothing. So at this point I'm quite concerned I'm responsible for my capital one card and also for the {$2400.00} on my XXXX XXXX card. Now right around the time XXXX bank announces they have merged or purchased XXXX XXXX, I start receiving mail and notices of changes and new mailing addresses etc. Not much I can do I've already initiated this transfer. I call capital one bank express my deep concern that my XXXX XXXX card still hasn't been paid off, but the balance is on my capital one card has the {$2400.00}. It's always the same thing jump through all the hoops verify my identity, etc. Then they act like wow it shows it was cashed back on XX/XX/XXXX, we sent the check to the address you provided, maybe you need to give it more time. Okay here we are XX/XX/XXXX! I requested a copy of the cashed check, I received it. I've been calling everyone on the face of the planet. The check was in deed written out to XXXX XXXX, with my account number, my address and info. However it's just stamped on the back for deposit with several numbers and bank entity names. I've called those institutions, and they won't help me because I don't have an account with them. I ask why are you depositing this check then they say you need to contact the issuer of the check, I say I have, they say it's my problem the check was cashed it's out of there hands, I've called XXXX XXXX, XXXX XXXX, XXXX  XXXX XXXX, XXXX XXXX, capital one bank, no one will help me. This should not be happening I've worked for 33 years as a XXXX, I low middle income I barely get buy, these credit organizations are taking advantage of me and others, I think Capital one is in the wrong here, because it seems they have performed a very unsound credit card transfer. Why are they writing a check in the first place? Why are they not looking out for me? They make me jump thru hoops everytime I call to validate my identity, why didn't they do that with XXXX XXXX? Why am I having to try to recover funds for there mistake? Why is it my fault? The address at the time was right. My account number was right, my name and address was Right. I want people to know this is going on! It indeed looks like I'm screwed! I'm being stuck with both bills. I've done nothing wrong! If I don't pay my credit that I have worked so hard to build would be ruined! I'm at a point where I hate these companies! They are selfish! Self serving! And only care about themselves, they lie to you get your money threaten to ruin you and no one can help us small people. Do not use these companies they are wicked!