Tmobile process done INCORRECTLY

Has this happened to anyone? 

I did an account transfer to my mom, in which my act was closed. (Dec'22)

Before the transfer my mom purchased a new phone. They didn't transfer my moms billing to the new account. So i was charged on my old account which still had my card info 

I called over the phone and was told i couldn’t be refunded because the account is closed. 

 Apparently the process when transferring was done wrong. I had to transfer my moms device over to the new account before closing. I was helped with both transferring acct and closing (since it couldn't be done at the t-mobile store) over the phone, so the person helping me have had to known that since the point was to transfer the acct (DEVICES AND ALL). 

I had NO idea they were going to charge me, i did not receive any statements for my last bill or ANYTHING. Plus i was charged in January too!!

When i log in online it goes straight to my moms new account. So there was no way for my to see my bill for January or Feb! I woke up to huge bill on my bank acct 

So now im stuck with a possible collection bill!! it's so frustrating that i had no idea of this bill. (Feb'23)