Logical???

Logic here makes no sense? In the early 2000's after being years already a client of FNB I actually app**** and got a credit card with them, and SIGNED A CONTRACT with a specific credit amount. From +/- 2015 my actual salary has been deposited into this account fully which meant I always paid whatever was due. But in 2020 during the pandemic FNB decided on their own accord to reduce this CONTRACTUAL amount without prior notice or even an email. After 2 months the bank increased this amount a bit BUT STILL NOT to the full CONTRACTUAL amount that was signed (just wondering here who is breaking the signed contract). As during the pandemic I still receive my FULL salary STILL PAID INTO THIS CREDIT CARD account. Received an sms today stating that my card to stay in "GOOD STANDING" that due to me unfortunately had to go over this amount by R190,00 to pay ASAP. As salary goes into this account for more that 10 years already and THE Bank breaking contract by reducing the SIGNED AMOUNT, I do not understand this logic. The bank does not even need to phone me as to explain as it in my mind is illogical as: 1. I did not break the contract by reducing the credit amount. 2. My salary goes into this account monthly for over 10 years already. 3. The amount over the reduced credit limit will be paid when salary gets deposited, as history shows. As stated I do not want to receive a sorry phone call.