Same Exact Thing Happened to ME:
Penfed Closd my account earlier last month. I received a similar letter and was completely dumbfounded. Because I had disputed and had the errors removed... Anyways, as soon as I found out I called their customer service number. The CSR said that there was nothing that he could do on his end unless I sent an email to their lending department as to why I wanted my account reopened/reinstated.I went ahead and explained to them my situation and why I belived the account was wrongly closed. A couple days later I called to checked on the status and was told that all the information that I had emailed them was correct but they were not going to reopen my credit card because the CSR said that "we never reopen credit cards".
However, I pressed on and asked for a supervisor/credit department to clarify as to why that was the policy. The CSR in the credit department was amazing and said that she will personally look into it and call back. A couple hours later I received a call from the same CSR in the credit department that was understand and she congruatulated and said that they had reopened my credit card.
All in all, PenFed is a great CU and will work with you, but you need to be able to get to the right department and really make them understand your situation. Good luck!