Complaint sub-issue: Problem during payment process

I got a credit card when XXXX. encouraged Co-op members to apply for a XXXX XXXX with U.S. Bank. That was in XX/XX/XXXX. There have been constant problems with using the website to make payments. At times, U.S. Bank would offer a survey and ask from an extensive list whether the user was experiencing certain problems. Problems I experienced included website not loading components before timing out, not loading personal image ( When setting up account, instructions are to abort log-in for security reasons if image does not appear ), loading misspelled placeholders such as " image 2 '' in place of personal image, payment button never working in any browser other than XXXX XXXX but issued not stating this, ; and REPEATED failure of the system once logged-in to process activity such as making payment or allowing to move up date of payment. Frequently system will suddenly issue message " System unavailable ''. I can appreciate this if there is a security breach, but it happens so much that by late XX/XX/XXXX to early XX/XX/XXXXit takes an average of 5 days for me to be able to log in and stay logged in to make payments. 
A problem of less concern is that the system will recently display " available credit {$0.00} 00 '' rather than calculate it. 
At present I have been unable to log in to make payments for 3 weeks, and am quite concerned about whether U.S. Bank has jeopardized the security of my account. 
More than a month ago I changed both my phone number and address online. The old phone and address were not terminated until XX/XX/XXXX, so I would have gotten anything sent to either. After that, mail was forwarded and old telephone was no longer my number. 
U.S. Bank sent an anti'theft notice of address change to my former address, just as my bank did. So I know that the change was received. However, it seems either U.S. Bank did not make the changes to account or it has otherwise jeopardized security of account. 
Every time I log in from new phone number, the system requires multiple security questions be answeredeven though I select " remember this number. These were initially questions I had at one time selected, but then 3 weeks ago it required answers to questions I do not remember ever seeing before. Multiple times the system prompted me for last 4 digits of SSN but then asked if I wanted verification code sent to ( former phone number ). Other times it asked whether I wanted verification code by telephone or e-mail. I selected the option thinking that then I would select a-mail. My a-mail address has not changed. But when I selected this option, then the screen display stated that a verification code had been sent to my primary phone number. I did not receive such code, and so it seems U.S. Bank is sending the code to someone else 's phone number. 

On addition to these problems, 2 months ago I was charged an interest charge that was miscalculated. There was a small portion of the balance from previous month unpaid and U.S. Bank apparently applied the 26.99 % interest rate in its entirety to the remaining balance for that one month rather than calculate the rate on an annualized basis, resulting in a huge interest charge for one month. I ask that this be recalculated correctly. 
I am very concerned about security and U.S. Bank 's ability to maintain its own system for those of us who are clients without placing our accounts and information at risk. 
I can not believe XXXX would have selected this financial institution for its members if it had known the risks we would experience.