Phone updated somehow now my authenticator is unlinked and its sending sms to an old cellphone number that was shutoff a year ago

So my iPhone updated the other night and I never use the authenticator because everything is saved on my PC. I play Heroes of The Storm and I’m on a team for Nexus Gaming Series and to log in to there website you need to log in to battle.net went to do that it sent the authenticator to my iPhone and I can’t get it. The only viable option I have is to send SMS but that goes to an old cell number I turned off because at&t had a deal buy a phone get one free if I got a new number or some bs like a year ago. I’m still able to play and stuff because I haven’t logged out but I’m worried this may become an issue where I’m locked out of my account and as I am staff for NGS as well I need to be able to log into the website to fulfill my duties. Please Help I know its Xmas eve I’m not expecting an answer tonight but soon would be great Thanks in advance.