Citibank Credit Card Complaint

Citibank Credit card department,

APR or interest rate Massachusetts

I did a kitchen remodel with the home depot, the designer told me I could open a home depot credit card interest free for 24 months. My interest free promotion ended in -/-/-. I have my credit card on autopay, as I do all my bills as not to miss a payment. The autopay on -/-/- was 7 times the usual amount so I looked up my account and saw that they added - in interest to my balance of -. After the shock I called them, furious, no warning from them about this and was told it was deferred for 24 months and had it explained to me. I wish it was explained to me when I signed everything for my new kitchen. I had a citi bank card and an - with o % promo balance for 12 months. The difference should have been explained, The home depot I went explained none of this. That deferred feature should have been pointed out, That is not truthful or fair business practices. The home depot customer service rep I had on the phone asked if i signed the contract, yes I did along with the kitchen remodeling contract, there were many papers and I trusted my kitchen designer at the home depot to disclose something as costly as this, he knew I was on a tight budget and we kept changing materials etc to lower costs, This can not be legal. I would like that interest reversed and I will pay the balance in full.