Poor Cellular coverage all of a sudden - Dropped calls and No internet, No service/Limited -Californ

As of a few months ago our AT&T cellular coverage has declined from 3-4 bars to now 1 sometimes 2 bars in Temecula, Murrieta and Winchester CA. We have had phone calls drop, text won't send or come through. Unable to use Maps or access email. The service had been great for years but all of a sudden within the past few months we can't get calls or texts or internet services in most areas in the cities we are in daily. This is even happening to us in the high desert in California (Hesperia, Victorville, Apple Valley, Big Bear)