Axis Bank changed ₹50k fee waiver to ₹3.5L after card issuance. Is this valid?

My IndianOil Axis Bank Credit Card was issued with a ₹50,000 annual spend requirement for fee waiver.

Axis Bank later increased the milestone to ₹3.5 lakh for existing cardholders. I spent ₹51,158.38, which meets the original ₹50,000 criterion, but the bank has denied the fee waiver based on the revised ₹3.5 lakh threshold.

Axis Bank has confirmed in writing that the original threshold was ₹50,000 for customers onboarded before 20 April 2024, but that it was subsequently revised to ₹3.5 lakh.

Can a bank unilaterally change an existing credit card's fee-waiver condition and apply the revised threshold to an existing customer without explicit consent?

Has anyone faced a similar issue with Axis Bank?