Is expiation required of one who swore not to take this month's internet subscription, then took it the next day after his friend told him, "Now I must take it"? And does this oath necessitate that he not take a subscription from him next month?

If by your oath you intended not to take the subscription at all, and then you took it, you have broken your oath and expiation is due. However, if you intended a specific day and took it after that day, you have not broken your oath.

If your intention was to honor your companion, not to obligate him, then the preponderant opinion is that expiation is not due.

One should not take oaths lightly or swear frequently, for Allah Almighty says: "And do not make Allah [an object] of your oaths."

Refraining from taking the subscription for the coming month is not sufficient as a substitute for expiation for the oath.