blockchain still provide a way to reset your two factor authentication by pressing a button on the left side of login form with alt "reset two factor authentication" you just need to give em a proof that you're owning the phone so you can simply call your career about this problem and they will probably give you some details or important document that may let you have the proof for resetting 2fa

just an advice it would be better if you'd enable 2fa through google auth and backup your qrcode as a image and then print it and save it somewhere so you'll not worried to lose it again, and google auth just need internet connection