I've read that many shuls have "cell phone lockers" to encourage people who come for praying to store their phones prior to entering the shul.
It's a great idea, but, many shuls don't have this, or don't want to spend money doing this. Regardless, it's nearly impossible to force everyone to turn off their phones or place it in a locker. As an alternative, I'm curious if anyone has invented a complete cell service "blocker" which will block out all web as well as phone service from both inbound and outbound calls, as well as all texts, WhatsApp, etc. It won't completely discourage people from using their cell phones, but, at least, if they can't have their phone's ring, it will be less noisy, and it may ultimately discourage such people from using the phones altogether while praying.