My account was changed without notification

I learned by inquiring about unusual data usage, that you had changed my account a few months prior without notifying me. "We no longer offer that plan" was the reason for the change. I'm not going to pay more for a comparable plan, so requested the account be closed. 

I had to call back a month later because you sent an account payment reminder email. Today, I stayed in the phone until the representative said the account closure was completed.

Following the last call, you sent an email requesting reason for the closure, without any way for me to receive a verification text to a closed account! 

(10+ year customer)