"Asking to leave WhatsApp is like cancelling your contract with yout ISP and going offline just because you don't like the company."
Hopefully the reason this is at the top is not this sentence.
This hallucinatory idea is exactly what Facebook PR, a.k.a. "damage control", wants people to believe.
You have no contract with Facebook. You pay them nothing. There is no legal recourse whatsoever. You cannot enforce "your end of the bargain" because Facebook undertakes no obligations to you.
Say what you want about the quality of your internet or cellular provider's service, etc., or how much you hate a company, but the fact is they have to fulfill their contractual obligations and provide service, they cannot just do whatever they want, whenever they want, as Facebook can.
If the internet/cellular provider does not deliver, then there is no Facebook. Whereas Facebook could disappear if their advertisers stop paying and the internet would still be here, because people would still be paying for internet access, and internet users would still use the internet to do all the same things they do now, and more.
Practically speaking, you may treat a tech company like a common carrier, like a telephone/internet/cellular provider. After all to the user it may seem no different. It is accessed through a "phone" and it seems to work like the service they pay for through an ISP or cellular provider.
But the minute you say this is like a "contract" you are submitting to pure delusion. You have no contract with Facebook as a user and you pay nothing. You're a product not a customer. Facebook has essentially zero exposure to liability from user complaints and that is why you are reading so many complaints about them, e.g., on HN. The best a user can do is rant into the aether and pound sand. There is no contract to enforce!
Then there is the absurdity of pretending that access to one company's computers is equivalent to access to the entire internet. This is like saying cancelling your subscription to AOL is like cancelling your account with your ISP. Today, no one is naive enough to equate AOL with the internet, as people once did. But Facebook believes people are naive enough to equate "Facebook" with "the internet". No doubt the AOL phenomena is a running joke at Facebook. The more things "change" the more they stay the same.
Do whatever you want, but let's refrain from propagating illusions that tech companies want people to believe.