apple two factor authentication

i went into an apple store back in 2014 and long story short, the apple guy tried to help me by setting my two factor authentication number to one of the demo phones at the store. no idea why he suggested that but it ended up using that phone number as my two factor authentication phone number and i have no idea what it is... im trying to access that email and I guess my question is, who do I contact to reset the two factor authentication? It's acting like the phone number is the only option but there has to be another way.