Hi there @Evgheni!
Thank you for bringing this matter to our attention! Utilizing your online access is definitely a helpful feature to take advantage of. I will be happy to advise some solutions to fix this problem.
In the case you are unable to access your online account; I always recommend trying an alternate browser first. For example if you are using Internet Explorer, try to login to your account using Mozilla FireFox. You can always clear your browser history by clearing cache and cookies. This can assist in fixing any minor glitches your browser is experiencing.
I would also recommend to logging into your account via the myAT&T app. This way, you can determine if your login information or the site is having issues.
I hope you have an amazing rest of your day and take care!
Shenoah, AT&T Community Specialist