As I wrote last week, one encountered a terrible problem when switching from iPhone to Android -- your phone number remained registered with the Apple iMessage servers as an iPhone and so that Apple tries to deliver texts from other iPhones to your new Android phone via their iMessage servers. That does not work, and so the text just disappears into the ether, with the sender thinking it went through fine but the new Android user never seeing it.
After months and months of problems, and at least one class action lawsuit, Apple now offers a fix. You can now de-register your phone number in the iMessage system by going to this link. I don't know if it works and I don't know if there is any time delay. I suddenly started receiving my texts from iPhones this weekend, about a week after I made the switch and called Apple to de-list me in their servers.
By the way, I tried to use the de-listing link. The process involves a text back. I never got a text back, lol. So I am not positive the de-listing link is actually working, but since I was successful (apparently) with it last week doing it using the old method, I am not worried. I was successful using the method at the bottom of this page.