i have got new t-mobile phones and somehow number is changed and i want to have my same

[Angel1]

old number..? today i went 2 t-mobile store to upgrade my lines and a REP told me if i change my numbers i will be saving a lot.. like $30 every month on my bill and wont be charge $19 somewhere or 18 upgrading fee.. and somehow i was ok but now i just want my same number back i dont know why but i like me old number!! is it possible to get that number? will they charge me or not.. will i be still able to get that $30 discount on my bill... thanks