Product: Credit card or prepaid card

I have been a satisfied customer of Capital One credit card products for many years. For several years I used one of my cards, which is branded Savor, for tens of thousands of dollars of expenditures in reliance on the companys promise that they would rebate a percentage of expenditures to me through the Savor Rewards program. 

I have an excellent credit history, and as they confirmed to me on the phone this morning I have been an excellent t customer because I always pay on time and even use another branded Capital One credit card. 

I tried to use my Savor card recently and found it blocked. I called customer service today to find out what was wrong and to unblock my card. It was explained to me that they supposedly wrote me a letter in late XXXX asking for additional credit information from me ( apparently they wanted to ascertain my current employment ), with a two week deadline before restricting my card. I would note that the other Capital One card I hold didnt require this information. 

The only written communications Ive had with the company since getting the card have been through text or email. My bills are received and paid on-line and I literally get no communications from the company via regular postal services except for further solicitations of cards or services. I received no other form of communication in this case before my account was restricted ( their term for having an account with a card that is no longer valid and an inability to access my rebates or rewards ). It is not even certain that I ever received the communication they claimed to have sent. First, it was sent to my billing address which I have been unable to physically visit since the letter was written. I get my mail forwarded, but I have zero recollection of ever seeing a letter from Capital One requesting information and my offices mail room has no recollection of forwarding me such a letter even though they forward everything. 

I have a credit balance on the account and over {$400.00} of rewards, and I learned from the customer service agent this morning that Capital One will refund the credit balance but that they will not compensate me for the {$400.00} plus of rewards earned by using their card. This seems like nothing other than an outright theft to me. Although the agents I spoke to on the phone were solicitous, they claimed there was nothing the company could do. 

If this theft happens to someone doing business with them with another card and with a perfect credit history, I cant imagine what happens to others with a lesser credit history. 

I dont care to ever do business with Capital One again if this is how they treat their best customers, but I do want my rewards refunded back to me as I relied on the companys agreement to effectively give me rebates in exchange for using their card in third-party transactions. 

I would add that this is an extremely harsh penalty even if the facts were as they stated them - they supposedly mailed me a letter on or about XX/XX/2020 demanding answers by XX/XX/2020 or else my account would be restricted and I could no longer access any earned rewards! Its worth noting that Capital One always texts, emails and occasionally calls when they suspect fraud occurred on my accounts. Why did no one try to reach me using their standard communications methods before they caused me to forfeit over {$400.00} in rewards? 

Thanks for any assistance. Again, if it happened to me with my excellent credit history, its not difficult to imagine this happens to others with other credit profiles. 

I would add documents to review but there is no history of written communications between Capital One and me!