Canadian Imperial Bank of Commerce [CIBC] review: Unethical practices with promotional offers

I received a balance transfer offer from CIBC for 0% for 10 months (due March 2026). I've made payments covering ALL my card transactions for the statement period and some more which I expect to go towards payment of the balance transfer. For some unscrupulous reason, I've been charged interest despite making payments that cover all my card transactions. I called into CIBC service center and I was told that my agreement, as told over the phone, was that any payments I make will be split between my card transactions balance and the balance transfer made. For real? Payment of the balance transfer is not due until MARCH 2026! I accepted this offer online and have NO DOCUMENTATION whatsoever of CIBC of the terms. This is a practice of CIBC that's so unscrupulous where you're given a promotional offer and you only get to see the terms (tiny prints) of the offer at the time of acceptance electronically.
Atop the above, the complaint portal on the CIBC website NEVER works. If you work into the branch, the staff are either clueless or not helpful.