It may be a coincidence but I've noticed these problems ever since upgrading from Nougat to Oreo 8.0 on my Moto Z Play.
It's not ALL the time but it enough to be REALLY annoying. Text and emails can take up to hours before i get them. Friend messaged me and it didn't show up till over an hour after he sent it thru Hangouts. Sister sent a message through WhatsApp and that took over an hour till I got it. Same with the stock Android message app.
Also calls not coming through. My sister called 3x the other day and I never heard the call or even had a notification that she called 3 times.
I already reset my network and all that stuff. Any ideas? It's become problematic...don't really want to leave Cricket but if Cricket is the problem then I have no option :(