What is the ruling on one who swore an oath not to transfer credit to anyone, then bought phone top-up cards for others or gave his wife money for her to buy the top-up cards herself?

The preponderant view is that intention is considered in oaths. So, if the oath is intended to mean something it could possibly mean, then the oath shifts to that meaning. If there is no intention, then one reverts to the cause of the oath and what prompted it. If that is also absent, then the oath is interpreted according to the apparent meaning of its wording. Accordingly, your oath was to refrain from transferring the balance only through the bank, and all other forms do not break your oath.

A conditional divorce takes effect upon the fulfillment of the condition, whether the intention was to effect the divorce or to threaten or to emphasize. Some scholars hold the view that if someone conditions his wife's divorce on a condition, and he did not intend divorce but rather intended emphasis, then if he breaks the condition, his divorce does not occur, but he is liable for an expiation for breaking an oath.