Citibank Credit Card Complaint

Citibank Credit card department,

Billing disputes California

I opened a bust buy credit card to earn 10 % cash back, when i received my credit card statement I went online and paid the balance due in full. The payment due date was -/-/2017 which was a Saturday, on Sunday -/-/- i paid the balance in full typically when a payment is due on a weekend you have until Monday to make the payment. Furthermore when I logged in on Sunday the balance due in full reflected the same amount as my statement. I paid the entire balance a figured that was it. I never received another statement. On -/-/- I received a message from the collections account stating I had a balance of $140.00. I called and they said I was emailed a statement on -/-/- which I did not receive, it was not in my spam either. When I logged in on Sunday -/-/- and paid the balance the account said was due in full of $4400.00 that should have been the final balance. Again I was 1 day late but it fell on a weekend even when that happens with my mortgage they waive the fee if Payment is received by Monday.