[tsac]

Without going into the need carriers have to make money, the features on most smart phones require the carrier to "unlock" various features. some lock data access and some restrict other features.

your trying to get your old phone to work on WIFI. When that phone was manufactured the various security levels and other features demanded by carriers were blocked to maintain security.

You either need a new phone or get a data plan for the one you have but don't be surprised if you need a data plan for any you choose.

One added thought, some carriers do not block a phone that "had" a data plan that unlocked the WIFI ability if the subscriber drops cell service