Product: Credit card or prepaid card

I applied ( and was approved ) .... 
My Chase freedom unlimited ( ending number on card is XXXX ), visa signature card offered a sign up bonus of {$150.00} IF you spent {$500.00} in purchases the first 3 months. 
I fully fulfilled my end of this contract. there was no problem & it stated, & thus, I was first awarded the {$500.00}. It then ran up to XXXX with other purchases & cashback rewards from use of card. 

MUST be noted, this card does NOT expire until XX/XX/XXXX. 
. 

I called the other day -- to be exact, XX/XX/XXXX -- as I was making updated notes on my credit cards ( I have 5 ), also thinking to activate the quarterly " bonus '' reward categories & to my utter shock, they told me they " closed '' my account & yes, furthermore, took back the money ( earned rewards ) they owed me. 

As you imagine I was flabbergasted, saying that's impossible, you can't do that. I outlined I have {$150.00} coming to me & most vitally it's not even CLOSE to date the card is to expire ( so yes, is blatant theft. We had a contract! Plus equally confusing is if I were out with JUST this card, and it's often I have only ONE card on me -- it would NOT work as they closed it all without notifying me! ). 

They said somewhere buried in their small print it states they can ( if card not used in a year ). I mean, there's been a pandemic on & our spending & finances have been horribly impacted like most others. Still, that shouldn't matter really! Again, this card does NOT expire ( OR Was NOT TO ) until XX/XX/XXXX. Over TWO years, I have the card right here! 

I do not see where, I looked up their terms, but also if that IS " buried '' in their small print, that is equally unethical, as it is not known to users ( I assure you ). 
That is NOT something to " bury '' ... .it 's a lot of money! 
They then tried to say they believe they sent me a letter of notification. 
I assure you NONE was received ( and our mail was more than spotty during pandemic ) as I would never EVER overlook a letter informing me a credit card I own was being closed due to NOT being used enough. 
Plus, no, other than choosing to spend that initial amount for sign up bonus -- and that is left to the person to do or not do! -- there were NO instructions on what ones " usage '' must be. it's vital to know if a card has annual fee or other conditions such as that. 

I have never in my life experienced something so overtly fraudulent & if not illegal ( I believe it is ), MOST egregiously unprincipled in my life. 

I will assume if this is allowed, they can ( are & WILL ) steal back literally hundreds of thousands ( if not millions ) of dollars doing this unsound practice to unsuspecting customers.

I DO have 2 other Chase credit cards and that is due to their approving me. They offer this sign up bonus of their own free will, no one put a XXXX to their head. 
If they did not want to honor their offers, the time to refuse doing so is when one applies, certainly NOT afterward. Actually refusing persons with stellar credit stores like me seems mildly unethical, again, IF not approved, then at least there's no real harm done. 

I believe I'm not only entitled to this money ( in fact, they even knew the exact figure -- {$150.00} -- without my stating it first so they are well aware they contracted it with me ) but they have NO leg to stand on for closing an active, in " good standing '' account just to overtly steal the money that was loaded on it. 

The representative I spoke with said she " understands '' my frustration, " wishes she could help me but can't! '' and lastly, she would pass on to supervisor to review & I'd get copy in my email that day of my case. I was generous in waiting more than that day on what is a very pressing matter to me. 
I had her read back my email address twice. Obviously since I'm here, NONE came. And in calling to follow up, another rep today said she had no notes or information on this card they closed. 

Please help me, I'm desperate & very alarmed something like this could even happen. I've closed a credit card account once ( as it was too hard to reach them for assistance ) & was immediately sent a check for what was due for my rewards. 
This just can't be! 

Also I've never ONCE paid late or caused any issues for them with this or any credit card Lastly please excuse all the massive detail but I wanted to error on side of comprehensive than to leave you with pending questions. 
Still that said, if you need ANY additional information, please don't hesitate to ask. 
Thank you so much. 

XXXX XXXX.