Product: Credit card or prepaid card

I am a Walmart card holder. Walmart card was controlled by XXXX XXXX Several months ago I noticed that my interest rate in my billing had been raised? I had received no notice. Then hints of Capital One being around? 
My Monthly bill, that I have always paid online, was due on XX/XX/2019. I paid the bill online on my Walmart account page on XX/XX/2019. I received a confirmation from Walmart that  morning,XX/XX/2019 at XXXX, that confirmed that the bill payment had been accepted and would be provided to my account on XX/XX/2019. 
As I always do with my card payments I follow my checking account online to make sure all my credit card accounts are paid for. 
No Walmart payment clearance on XX/XX/XXXX,XX/XX/XXXX,XX/XX/XXXX? 
On XX/XX/2019 I received a notice from Capital One that my payment to my Walmart account was overdue?

This was news to me that I would receive notice from Capital One about my Walmart card?

I placed a call to Capital One which of course lead to poor phone reception in the XXXX. XXXX the customer service rep could offer no explanations, except that the change from XXXX XXXX to Capital One had caused a blackout from XX/XX/2019 to XX/XX/2019. 
Notice the convenience of the time period of the blackout? My payment online date and my due date. 
XXXX ( Capital One customer service ) attempted to explain poorly that the easiest way for me to take care of this was to make another payment without regard to investigating what had happened to my payment that was guaranteed by Walmart. His only conclusion was that I had not made a payment since it was not showing in my checking account and he would be glad to handle a payment for me via phone. I became enraged as I saw this as a way to shake money out of me without attempting to resolve the issue? He did as threatened and hung up the phone on me. Deserting from the performance of his job. Phone reception was terrible, talking with Philippine operators sounding like they are talking in a fishbowl. I called again and with this operator ( XXXX  ; fishbowl distortion ) I requested to speak with someone in the US. I was transferred to XXXX in VA. Explained the situation and was again given the same run around. She would assist with me making another payment. Again stating that I had already made a payment and where was it ; the fact of the blackout was introduced again? I again restated that I had confirmation of payment but she stated that since had not been pulled from my account that the payment most likely had been lost? The person XXXX had no proof that this was a result? I stated that if there was a B/O on XX/XX/2019 then how was I able to receive a confirmation from Walmart that payment had been made. Silence followed by do want to make payment arrangements or not? I became infuriated as Capital One customer service was proving that they would not take steps to investigate what happened to my payment and if I had confirmation of payment why wouldn't the payment be applied to my account?

Also during these conversations there were constant references by me as to why was Capital One in the picture and was told that mailings and emails had been sent saying that this change was taking place. 
I have received nothing in mail? I have checked back emails. I have nothing. No notices what-so-ever? 
In my anger I threatened to contact FTC! That brought responses. I was informed I was being transferred to a supervisor. A threat finally got a response. That's poor business. 
So now the 5 minute wait for a supervisor. This is nearly 45 minutes on the phone now. 
XXXX came on the phone ; a supervisor. " Oh this shouldn't have happened to me. Oh we can straighten out this matter. I can understand your anger '' XXXX again reiterates that notices were provided to customers. 
I deny that I have received anything? 
He says with the B/O, what the problem has been, that with the Indigenous People holiday, everything has been thrown off by two days. 
I don't understand what that means? 
XXXX can't understand how I received confirmation of payment when a B/O? 
( I read the confirmation I was sent, to him ). 
I don't understand or care of their screw-ups. 
He says correspondence has been sent out? 
I say I have received nothing ... ... silence on other end of phone? 
Finally XXXX says well best for you to wait two days and this should be resolved as we should have the payment.

I state but your customer service people were trying to get me to make a payment over the phone.

He states " Oh that's not necessary. Your payment should clear in two days.

I say ; " that's what you say. Then your customer service people were attempting to get an additional payment out of me. Trying to get me to make a payment without an investigation of the previous payment ''. 
XXXX states " they shouldn't have done that ''? 
I agree. 
I ask were they ( customer service ) or have they been informed of this blackout problem? 
His return answer is " I don't know ''? 
This response made me so angry. It shows the lack of business professionalism that is rampant in companies with these overseas operators. 
No responsibility is taken and a lot is lost in the language barriers. 
I say so what do we do? 
He responds we wait the two days?

Again that does not address my issue to resolve this problem with me having a confirmation of payment. 
Afternoon of XX/XX/2019 I finally receive an email announcing that Capital One and Walmart have combined credit card.

I have a contract with Walmart ; I have not agreed to a contract with Capital One?

My due date since being with Walmart has been XXXX of each month. 
Capital One changes my due date to 19th of month without my permission or any discussion or correspondence.

I am very against Capital One. I find them to be an underhanded corporation. I have an auto loan with Capital One plus another credit card, both of which I have been very disappointed with. My goal as been to pay off both and be done with Capital One but Walmart has done a backdoor deal with them going around it's customers and treating their customers with great disrespect. Now I have another Capital One credit card that I don't want.

Fraud comes to mind as two different customer service people were trying to get another payment out of me. So in conversation with XXXX I would have been out two payments because of lack of communication between Capital One employees. That's fraud. 
XX/XX/2019. I go to my local Walmart to make a purchase using my Walmart card and find it is denied. I go to customer service desk enraged to find that the employees of Walmart have not been informed of the change or the B/O. The Walmart employees have been suffering for several days as people have approached them enraged that Capital One is now a credit card of no choice for Walmart. 
This is all highly suspicious?