Product: Checking or savings account

I am a client of Umpqua Bank who opened an account the XXXX of last year ( XXXX  ) in an Oregon branch office of the now-merged Columbia Bank . I'm an XXXX  citizen, now residing in XXXX for studying reasons. 
I opened this account to cash checks for a seasonal job ( I worked in a XXXX  in XXXX XXXX, OR ) and didnt close it after I left the US because it was necessary to get my tax refund by the IRS . 

The above-mentioned account is now locked because I failed the authentication process via XXXX email. This is probably since I used my US residence address when authenticating instead of my US workplace address. This is without doubt my error, but the problem is that the person I was speaking with at that moment forgot to mention that failing the procedure would result in the locking of my account. Knowing that I would have never tried before being sure of the information I was providing. 
( Just to be clear I want to say that the reason I needed to authenticate myself with a special procedure to access my account was that I could no more use the XXXX  number sent to my old US phone number since I went back to my usual XXXX  phone number ). 

After that, it was said to me that the only option to unlock my account was to authenticate myself by going physically to an Umpqua Bank branch office with my identification documents. 
In the past two months I called customer service several times and even a branch office in XXXX, OR, trying to explain that flying to the US just to solve this problem was not an option for me. 
I also proposed as a solution an online meeting with webcam so that I could demonstrate my identity and show my IDs ( I know for a fact that this type of authentication is common procedure among other financial institutions ). Both the customer service and branch office told me that that wasnt an option and that I still had to physically go to the US despite me being several thousand miles away from the closest branch. 

But then I was told by an employee of the branch office in XXXX that there is the option of closing my account and getting my money back if I sent a physical letter to the bank requesting the closure of my account. I specifically asked if I could do this even if my account was frozen and he replied positively. I want to be clear that the employee of the branch office I talked to said that just my signature was needed for this, but I provided all the information I could so that I can be assured that my account will be closed, and I would get my money back. More specifically, I attached a copy of my passport and driving licence, along all my personal data regarding the bank account. 
I also wrote to them that they could contact me via e-mail if they had any kind of problems. 

Two weeks after sending the mail I still didn't get any answer, both via mail or e-mail, so I tried to call costumer service. They said that they have no way of knowing if they received the mail and they can not give me anymore information since my account is frozen. 
I'm now at a point where I tried everything I can to access my account, but never got any help in return. In fact, since the first time I called them it only made things worse.