Italian to English Bus/Financial Law: Contract(s)

I am translating an offer from a mobile phone provider for subscription to one of their phone plans. (it is a "Proposta di Sottoscrizione").

My question is whether "adesione" can be translated as "subscription" in this context, as in Terms and Conditions of Subscription to XXX" or if there is a more appropriate term (like Agreement or Acceptance)

Another example:

"Il soggetto sotto identificato, autorizzato dall’azienda sotto indicata, propone a XXX di ***aderire*** all’Opzione XXX secondo le condizioni di ***adesione*** allegate alla presente"

Even here I would tend to use "to subscribe to" for "aderire a"

Thanks for your input!