If you're using
any service that's absolutely required for business, then you must be prepared for when they'll pull it from your feet or increase the pricing to eat all your profit margin.
Of course you need to prepare for that, that's just basic part of running any business, software or not. The answer to "why use that service to begin with if an alternative exists?" is likely based on cost or quality, but if it's required for your business and you can't switch to an alternative within 1 year, then you obviously knew that you should have had started looking for an alternative long ago and start preparations for switching to an alternative, from day one or, more precisely, from the day you decided that this business is worth running at all. The only excuse not to do that if it's a commodity product with clear drop-in substitutes, otherwise you're just sloppy with running a business and/or knowingly taking on risks that your business may suddenly stop - and not because of the API going away (the risk was predictable) but because of your own unpreparedness.
It's the same with any other services. What do you do if your landlord dumps you or the building burns down or goes down in a flood or hurricane or whatever? If your need for facilities is a commodity in a liquid market, then you'll be able to replace them, but if not, if you need something that's not readily available to avoid huge losses then it's your (assuming executive positions) duty to prepare alternatives in time and/or get appropriate insurance. What do you do if your service for accepting credit cards stops working or dumps you for whatever reason? If you're a reasonable business, you have a second, independent contract with all the deals already arranged that you can switch to in a day if not immediately. The same goes for any non-commodity that you need. If a supplier dumping you means just that you have to drive to a store and buy the same thing from someone else more expensively, then you can skip worrying, but if not, then it's on you to safeguard your business with alternatives instead of blaming suppliers for being unreliable. In some cases, the suppliers will actively exploit knowing that you don't have prepared alternatives - if they've got you by the balls, they can squeeze them and get the price and conditions that they want; and if/when you get serious alternatives, then you can get a whole new range of discounts, that's business as usual.