Product: Credit card or prepaid card

My wife and I had a consolidation loan, checking acct with TD Bank. Last XX/XX/XXXX we went into the local branch to conduct some business and the representative asked us if we were interested in a credit card. They said if we spent so much we would get {$150.00} back. This sounded interesting. When they ran my credit, I was awarded a credit card with a {$20000.00} limit and my wife was awarded one with {$7800.00}. I was shocked because I know I have a lot of things going on with finances. She said we could consolidate debt, take a cruise, etc. So based on all this information she sold us on, we accepted the terms. 
So I used my card to payoff 2 credit cards which was about {$7500.00} and put another {$5000.00} on the card for about {$12000.00} in use. 
Then around XX/XX/XXXXof this year they send me a letter saying they ran my credit and based on that, they would have to reduce my credit limit to {$13000.00}. They also said another reason was I was delinquent on my last payment. Delinquent, excuse me! Delinquent is when you are more than 30 days late not 4 days late. I happened to be sick during that time is the reason It was 4 days late. 
This Bank sold me a bill of goods to open up two new credit card accounts. I expected them to honor that obligation. 
If you look at the reason my credit score was what it was when they not only approved me for a credit card but for {$20000.00}, it pretty much matches the reasons they now say they have to reduce my credit limit. Yes my score is lower but it's still good. 
It's ironic, I had a consolidation loan with this bank and they give me a credit card. I actually paid off the consolidation loan prior to them reducing my credit limit. 
I'm sick and tired of financial institutions playing XXXX with folks. They seem to do whatever they want without a penalty yet the honorable consumer gets screwed. 
Yes I put money on that card, we're in the process of fixing up our house to sell it. Isn't that why I have a card is to use it when I need to? 
I have done nothing to this bank to place any doubt on whether I can honor my obligations because I always pay my bills. But my bank has now turned against me and reduced my credit limit. I was at a 63 % debt ratio and by them reducing my credit limit that has changed to 93 %. This will certainly cause my score to drop even further. 
If we sell our house in the next 2-3 months, I will be shopping for a mortgage and now by TD bank actions, my score will be even lowered which may affect what kind of loans we can get. I feel betrayed by this bank. The ironic thing is despite our circumstances this bank still sends My wife and me mailers to do business. 
There is something seriously wrong here when Financial Institutions can play XXXX with peoples credit scores. They sold us a bill of goods for us to open up credit card accounts. I have honored my obligations and they have reneged on theres. 
Their actions are going to lower my credit score even lower which is what I don't need now. I have done nothing to deserve this. I have fulfilled all my obligations with this bank. 
I currently have a checking account and this credit card account with them. I had a consolidation loan with them which I paid off ahead of time and this is how this bank chooses to treat this customer. They should be ashamed of themselves.