Trouble using your card: Credit card

I have had a Home Depot credit card for a few years. Which I have maintained a good balance, keeping my balance low. Ive received several invites to increase my usage, but chose not to. Due to illness, I missed a payment, but paid within 5 days past the due date to then learn that my limit was decreased to $200.00. Ive never spent over $350.00 on this card as I exercised financial responsibility. I was told all of the credit report stuff was the reason which makes no sense, as there are freezes on each of my accounts with each credit agency. How could they pull a report if there is a freeze on my credit? I requested that my increase be returned & was denied without any logical explanation.