You are mixing up two very different things.
-Error 53 is an account suspension for some sort of violation, often Auction House or transaction related. To fix this you have to put in a ticket to appeal and sort out what happened. https://us.battle.net/support/en/article/how-to-appeal
-Account locked due to a change in access pattern is COMPLETELY different and is not a punishment. That is due, as it says, to a change in IP or computer hardware. All you have to do to fix that is change your password using your secret question. That won't work though if you are actually suspended with an error 53. Did you see that "account locked due to change in access pattern" message when you logged in to game or only in an email?
I ask, because if you got a phishing email about a change in access pattern, clicked it, gave away your password and secret question....then that would explain the error 53 suspension. It would mean hackers got your account info and then did bad things with it.
So, lets start by having you appeal the suspension using the link I gave you. If you think you were hacked, say so in the ticket.
While that ticket is processing, I need you to do the following (most of this is good practice even if you are not hacked!)
1. Download, install, and update Malwarebytes (free version is fine). Boot into safe mode and run a FULL (not quick version) scan with the game up and gibberish in the login fields. Some malware only activates under those conditions.
2. When that scan is done, run a FULL virus scan with an updated virus scanner. Microsoft Security Essentials is free and decent these days. Better than Nortons, MacAffee, etc.
3. From a PC you know to be free of malware, change your email password. Check it for forwarding as well. Sometimes hackers get into your email as well. When done, change your battle.net account password one more time just to be sure it was done from a clean PC.
4. Create a new email that you use ONLY for battle.net and switch to it. Gmail is great because you can put two factor authentication on it and prevent hackers from logging in without a code. This way the hackers can't send you phishing spam.
5. Get an Authenticator!!!! The mobile device version is FREE and the keychain is only $6.50 in the US with free shipping.
6. Consider SMS Protect - this is not an Authenticator, but is a messaging service that lets you know about account changes and prevents some of them, such as an unauthorized email change. It can also be used to gain access if you get an account lock for an IP change.