My Mortgage recently assumed by Selene

My VA mortgage was just assumed/assigned to Selene Finance on 9/3/2024.  Have recieved no correspondence from SF, made my first call to SF on 9/9/2024 to ascertain How to make my monthly mortgage payments?? Learned my account was not eligible for online payments???  I have had my mortgage for over 5 years, never missed a payment not in distress, why was my loan sold to or assumed by Selene.  When I called to inquire what is my loan number? How to make my monthly payments?  I was hung up on? What do I or can I do?  How to deal with this company this last couple days has become a nightmare.  I am a senior citizen, 100% disabled VET more than capable willing to pay mortgage. I am in no way in financial distress!!!  What can I do??