Change Bank Accounts for Credit Cards

I changed a bank account for credit cards to the current primary one. I created a new bank account in the last year and then started to use it as a primary one. I was happy to change the primary account because the app for the new account is easy to use, and the transfer fee is very low. However, I had not changed bank accounts for credit cards to a new one because the procedure seemed to take some time. That was very unuseful since I had to store enough money for two accounts. For example, when I need to use large amounts of money, I have to transfer an account to the other.

Today, I did a procedure to change bank accounts to solve this problem. I had three credit cards; the first one was main, the second one was for paying the house fee, and the last one was unused. At first, I canceled the unused one. There were two cards rest. I could change the bank account for the card for the house fee on the internet, but I had to write an application physically for the main card. I did the procedure to get the application, and now I am waiting to receive it. I was very sad that I couldn't complete it online. I think it is an old fashion, and all procedures have to be completed online. Anyway, the whole procedure is not completed but is almost done.