best dishes at the taste restaurant on norwegian epic ship how to offer multiple payments and assure getting paid in ...

In the past few years, I have watched many sales webinars of various products and services at various price points.
When it comes to seeing prices ranging from $997 to $1997 or even higher, the seller offers
Pay the full price at a slightly higher price point and pay the option for 3 or 4 months.
I can understand how sellers guarantee payment when offering SAAS products.
How do these sellers guarantee the remaining payment when offering delivered products?
Anyone can cancel the regular payment on PayPal at any time, as can the scheduled credit card payment.
Do you know where to find some good information about this topic?
Thank you in advance.